The Top Ten Blog: Physics is in the house!

In this blog, I'm going to attempt to make a top ten list of the physics concepts seen in the household. The list is in no particular order.

1. Motors- Found in fans used to cool the house. Uses the concept that a current carrying wire inside of a magnetic field produces a force. The coil of wire inside, let's say the fan, is supplied with a current from the outlet on the wall, then there is a magnet inside that creates a magnetic field. This causes a force on the wire, producing a spin, thus causing the fan to rotate and cool your home.

2. Electric Potential Difference- IN ORDER for current to flow from the wall outlet to your appliances there must be an electric potential difference. With no electric potential difference your appliances will not be powered.

3. Lightning Rods- Pointy pieces of metal located on roofs that leads to the ground in order to ground the charge from the lightning. Now, I understand these are not found on every house, but they are very important and in the future I think they will become mandatory on every house. They work because scientists discovered that positive charges group up in the points of objects. The negatively charged clouds send a charge down (lightning) that is the grounded. Making it completely harmless and protecting your home.

4. Parallel Circuits-An electrical circuit in which electrical devices are connected in such a way that the same voltage acts across each one, and any single one completes the circuit independently of the other (Paul G. Hewitt). This is how your appliances are wired; so that when one malfunctions the others will remain on. 
5. Transformers- Use alternating current to crate a change in the magnetic field so charges can be transferred across the primary and secondary coils, either increasing or decreasing the voltage. They are used in computers and phone chargers to make sure they do not receive too much voltage.

6. Alternating Current- Found in every thing other than batteries. The electrically charged particles repeatedly reverse directions, vibrating about fixed positions. In the U.S the vibrational rate is 60 Hz.

7. Direct Current-The electrically charged particles flow in one direction. Used on those duracells and energizers we use, in which the current flow from a negative to positive end. Batteries are basically the only things you will find with this type if current.

8.  Fuses- Used to make sure your appliances are not flooded with too much current. Fuses are wired to the parallel circuits in your home by a series circuit, so when the fuse blows because it received too much current, it will shut down the whole system. In a series circuit each appliance is dependent on each other to complete the circuit. A fuse can be seen as a home's security system against too much current.

9. Charges inside a dryer- This is just a fun one, not that useful. But, have you ever wondered why your clothes stick together after being in the dryer? It’s because as they rub together they steal electrons from each other and become charged. Leaving some positively charged and others negatively charged, since like charges attract they stick together.

10. Outlets (American vs. European)- American outlets provide 120 volts and European outlets supply 220 volts. We cannot use our appliances in European outlets because they will supply our appliances with way too much current, causing them to malfunction. But they can use ours; their appliances will just be less efficient.

All of these physics concepts explain why stuff in your household happens the way it does, such as your clothes sticking together, or they contribute in keeping your home comfy and on smooth running machine (maybe that's not a proper term since we aren't talking about doing any work).

             

Unit 8 Reflection

Unit 8 was by far the most attractive unit yet. It was all about magnets, magnetic fields, and how we can use them in relation to electric fields. Paul G. Hewitt defines magnetic force in this way:

1. Between magnets, it is the attraction of unlike magnetic poles for each other and the repulsion between like magnetic poles.
2. Between a magnetic field (the region of magnetic influence around a magnetic pole or moving charged particle) and a moving charged particle, it is a deflecting force due to the motion of the particle: The deflecting force is perpendicular to the velocity of the particle and perpendicular to the magnetic field lines. This force is greatest when the charged particle moves perpendicular to the field lines and is smallest (zero) when it moves parallel to the field lines. 

Thanks Mr. Hewitt!

After we learn that stuff we can begin to apply these concepts to real life. So, when a paper clip becomes magnetized by a magnet what is exactly happening? First off it is useful to know that magnetic fields always travel from north to south inside of a magnet.
 


 
The paperclip has charged particles inside of it and once it comes close to the magnet the domain of the paperclip aligns with the poles allowing it to become magnetized. The paperclip will become magnetized whether it comes into contact with the north or south pole because the domain will just shift.
There are things called electromagnets which is just a magnet that is produced by electric current. Usually in the form of a wire coil with a piece of iron inside the coil. This also goes along with the fact that current carrying wires inside a magnet field feel a force. Electromagnetic induction is the induction of a voltage when a magnetic field changes with time.
We used these concepts in the motors we built, which you can read in my previous motor blog @dorianakamrphysics.blogger.com
Transformers and Generators come next. As I learned from my fellow physicist Paul Jordan, a generator is basically a reverse motor. It uses mechanical energy to create electrical energy by turning a coil of wire within a magnetic field. A transformer either lessons or increases the voltage to an appliance using coils of wire. But I think Wes and Jared explained this better.

 Equations from video: Primary Voltage/# of coils = Secondary Voltage/ # of coils (for transformers) ; Power in = Power out

 

The things that I found difficult in this section was explaining the magnetic field around the earth and why the cosmic rays are stronger at the poles. Just now have I grasped then fact that it is because the magnetic force is stronger there and they can not enter on the sides, because the magnetic field runs parallel to the earth. The problem solving skills came in we had to find how many coils were in the primary and secondary coils of a transformer. It helped me learn how to better cross multiply. This unit applies to real life because things such as computers use transformers, and credit card scanners use electromagnetic induction.

 

Physics Photo Project

         How A Light Bulb Works

 The picture I chose to take is simple, but shows one of the most useful everyday physics concepts. My picture is of a light bulb being lit. So how does a light bulb work? First off, the light bulb is connected to the wall, which supplies it with a voltage, creating an electric potential difference, therefore allowing a current to flow. The energy from the wall socket travels into the light bulb heating up the tungsten filament. It is very similar to molten steel, which glows white hot when heated up. However, if the energy from the wall socket heated up the tungsten filament in open air with the presence of oxygen it would simply burn away. Which is why the filament is encased in glass that has had the oxygen sucked out of it. But what exactly causes the filament to heat up and produce light? It is a principle known as resistance, or an objects unwillingness to let the current flow through it. The filament tries to retain the electrons as they pass through, so they must be forced to travel inside of the filament. This force provides heat, which is released and creates the light we see. On top of the light bulb you can see that it is labeled sixty watt and one-hundred twenty volt. The sixty watts is the power, which equals current x voltage (voltage needed is one-hundred twenty). Furthermore, current equals voltage divided by resistance. These are the equations needed to figure out just how much current and resistance the light bulb has. In this case the current is 0.5 amps and the resistance is 240 ohms because the voltage is 120 and the current is 0.5 If we manipulate the equation current equals voltage over resistance, or ohms law we get the answer for resistance. That right there is the basics of a basic light bulb.

Motor Blog

I just finished creating my own working motor in physics class, which was very exciting! The components used to make up the motor were two paperclips, a magnet, copper wire, and a battery. The battery is used to supply electrical current to the paperclips, which not only act as holders for the motor loop (copper wire), but the paperclips also allow the current to flow into the copper wire. The magnet of course supplies the system with a magnetic field, and lastly the copper wire is the motor loop that spins and makes the motor functional. All of these parts must combine to get the system to work. The current from the battery flows to the paperclips, which then allow it to enter the armature of the motor loop at the scraped parts. Which were scraped down to the silvery inside at specific places. They were scraped in a place where the loop would be in a vertical position on the paperclips. This is so the direction of the magnetic field and the current would line up and cause forces on each side that would cause it to spin. Using the x, y, and z coordinates to predict the direction the force would be in. I had to make sure I scraped them in a way that wouldn't prevent the spin and would allow it to make a circular motion. Once the motor loop is electrically charged and is inside the magnetic field created by the magnetic, we learned that this causes motion. Motors like the one I created are used in every day things, such as fans and automobile motors.
Here is a link to my working motor: http://www.youtube.com/watch?v=DgRNQh-S1Y4

Unit 7 Reflection

Unit 7 was all about electricity. The first things we had to get straight was positive a negative charges and the ways in which they work. Important things to know are that the positive charges are called protons, and the negative charges are called electrons. Opposite charges attract each other and like charges repel each. Usually when charges move they are electrons, because they are freer to move due to the fact that they are not bound to the nucleus like protons. Lastly, similar to the conservation of matter, electric charge can neither be created nor destroyed.

Now we can learn about Coloumb’s Law, which is  F=k(q₁q₂)/d². Which shows that electrical force decreases inversely as the square of distance between charged bodies.

Since we’ve got that out of the way we can talk about conductors, semiconductors, insulators, and superconductors.

1.     Conductors: Any material having free charged particles that easily flow through it when an electric force acts on them.

2.     Insulator: A material without free charged particles and through which charges do not easily flow.

3.     Semiconductor: Properties of a conductor and insulator; resistance can be affected by adding impurities.

4.     Superconductor: A material that is a perfect conductor, with zero resistance to the flow of charge.

There are multiple ways to charge an object, or transfer charges form one to another.

1.     By contact or friction:  Transfer by rubbing or simply touching.

2.     Induction: Redistribution of electric charges in and on objects by the electric influence of a charged object close but not by contact. For example, this is how lightning is caused.

           

Negative charges in the clouds cause the negative charges in the neutrally charged ground to move away leaving only positive charges at the surface. The ground becomes electrically polarized, which means that like charges are aligned with each other.

Since opposite charges attract, electricity runs to the ground. This is lightning.

Next up are electric fields, which one can see an illustration of above. An electric force per unit charge, and the inverse-square law can be applied to it.

The equation for an electric field is; electric field= F/q.

When dealing with electric fields there is something called electric potential, which is often called voltage. This is the electric potential per unit charge. To find voltage you use the equation, voltage= electric potential energy/ charge.  The electric potential in the equation is the energy a charged object possesses by virtue of its location. This all relates to the flow of electric charges, also known as current, and here’s how. In order for current to flow or charges to flow from on place to another there must first be an electric potential difference. So object A and object B must have differing electric potentials in order to start the whole process. When dealing with current there is something known as resistance (measured in ohms). Electric resistance is the property of a material that resists electric current. Ways to increase resistance are:

·      Thickness

·      Length

·      Temperature

·      Material

Now that we’ve learned that we can move on to finding the current in a circuit. The equation to find this is known as Ohm’s Law, which can be written as current=voltage/resistance (the unit of measurement is amps).

There are two types of currents:

1.     Direct current (dc): electrically charged particles flow in one direction. This type of current is used in batteries.

2.     Alternating current (ac): electrically charged particles that repeatedly reverse directions, or vibrate. Used in homes and mostly everything else besides batteries.

Current and voltage can be used to find electric power, which is the rate of energy transfer, or the rate of doing work. Power=current x voltage.

Lastly, there are two types of circuits, series and parallel.  A series circuit is an electrical circuit in which the devices are connected along a single wire such that the same electrical current exists in all of them. However, in a series circuit when one of the devices are disconnected they all go off. Also, as more devices are added the resistance increases, therefore reducing the current. Parallel circuits are electrical circuits that are connected in such a way that the same voltage acts across each one, and any single one completes the circuit independently. So, when one device is disconnected the others stay on, which is why this type of circuiting is used in households. When one appliance goes out the others will stay on. Fuses are used in homes to protect appliances. They control the flow of current and are connected to the parallel circuits in a series. When too much current gets to the fuse it blows, causing the whole system to shut off, saving your appliances from too much current that could cause damage.

Reflection:

 Some things I found difficult in this unit was the concept of an electrical field. At first, it was hard for me to get a grasp of what exactly they were. But, after being shown some illustrations I finally got a hold on it. Until we then brought in the ideas of electric potential and electric potential energy, which I have no idea why scientist would give them the same names. After, I finally got that straight I was fine for the rest of the unit. When doing the calculations, I learned how to manipulate the equation for Ohm’s Law or current = voltage/resistance so that I could find the voltage or resistance, when given the current. Then using this to find the power, which equals current x voltage. As I showed many examples of this unit relates completely to real life situations.

Unit 6 Reflection

Unit 6 was one of my favorite units so far this year. We learned about work, potential energy, kinetic energy, and many other things. First I’m going to talk about work, work=forcexdistance. The proper definition is; the product of a force and distance moved by the force. One thing to know is that in order for something to be doing work on an object the force and distance must be parallel. In other words, if you are carrying a 10 Newton book and walking a distance of 20 meters you are doing no work on the book. But if you push the book along the ground you will be doing 200 Joules of work (Joules is the standard measure for work). While talking about work we must talk about power, power=work done/time interval. Basically, the amount of time in which work is done, power is measured in watts.

Next came energy, which is defined as the property of a system that allows it to do work. We talked about potential and kinetic energy. Potential energy is present the energy that an object possesses because of its position. When an object has potential energy it is at rest, the equation for potential energy is PE= mass x gravity x height. The next type is kinetic energy, which is the energy of motion. The equation is KE= ½ Mass x velocity squared. A roller coaster is a good example of both because, the first hill is always the largest in order to get the most potential energy so when transferred to kinetic energy there will be enough to make it up the next hill.

The work energy theorem states that the work done on an object equals the change I kinetic energy (change in KE = work).

            Machines were the last thing that we talked about. A machine is a device used to increase or decrease the force you need to put in, in order to do a certain amount of work. One thing that is important when dealing with machines is the Law of Conservation of Energy, meaning that the work you put in equals the work put out (forcexdistance in = forcexdistance out). A machine lessens the force you need to put in to do this work by increasing the distance, therefore making your job easier. For example, when using a jack you only have to apply a little bit of force, but you must pump it a lot to only make the car move up a little (you increased the distance). A jack is a type of lever. The last thing you must know when dealing with machines is efficiency, or work output/work input. If a machine is 100% efficient that means that all of the energy was transferred and none was released. Efficiency is basically the percentage of energy you got out of what you put in.

            One thing that was difficult for me to understand at first was the idea that machines don’t change the amount of work you do. I felt as though machines made it to where you needed to do less work on an object and that’s why they made things easier. However, as I explained above they actually increase the distance, which decreases the force, thus making it easier to do the work. Problem solving was a big part of this section because all of the equations were related. We were presented with questions that gave us a mass of an object, the speed at which is was travelling, the speed it sped up to, and the distance it traveled. Then the questions had several parts. First we had to find the change in kinetic energy. Then the work done, which you had to know equals the change in kinetic energy. Next the amount of force applied, which you had to know the distance travelled and the work done, so you could use the work formula. Lastly, you were given a time in which this work occurred and you had to find the power. So, it was crucial that we had a solid understanding of how these formulas related. These concepts apply to real life for me, because they really helped me learn why things like jacks and pulleys work so effectively and how I could use this knowledge in the future to move heavy objects.

Mouse Trap Car Final Blog!!!!

As Race Day concluded, Paul and I came out victorious. There are a couple things that we had to account for in order to make a winning car. The first thing was Newton's First Law; an object in motion will remain in motion unless acted on by an outside force. Because of this law, we had to make sure we could decrease the presence of outside forces as much as possible. So, when the axle was jamming against the eyelets we used to hold it, we had to remove some of the tape to make sure this stopped happening. This prevented the forward motion of the axle from being hindered; therefore giving us smooth rotations, resulting in more speed. Also, we reduced the amount of friction acting upon the wheels by applying duct tape to the rims (CDs). The next thing we had to wrestle with was Newton’s Second Law; a=fnet/m. Paul and I made sure that we had the most acceleration that we could possibly create. So, we built a frame that has a small mass, using only paint stirrers as our bass. Then to get a large net force we built a lever-arm that is about 18 inches to get the most force that we could achieve. With the net force going up and the mass going down, we were able to get a pretty substantial amount of acceleration. Newton’s Third Law also came into effect, because it says every action has an equal and opposite reaction.  We figured out that the same force that the lever and string applied to the axle was transferred the wheels. The more force the lever creates, the more force applied to the axle, and then the more force on the wheels, creating more speed.

                The two types of friction present were surface friction and wind resistance. So, Paul and I had to make sure that we made the most aerodynamic car possible. to combat the wind resistance we made a slim, streamlined car. A bulky car would create more wind resistance and slow down the car. However, not all friction is bad. Surface friction between the floor and our wheels could actually help when we are trying to propel our car forward. By applying duct tape to the wheels we were able to get more surface friction, so our wheels would gain ground as soon as they began spinning. The only other problem related to friction was making sure that our axle stayed in place, keeping it from creating friction between it and the screw holders. That would decrease the force that was transferred to the wheels. All we did was apply duct tape on the axle to keep it from sliding in order to fix this, and then it was off to the races!

              As far as the wheels go, we decided to use blank disks. We chose these for a number of reasons. First because there mass is distributed evenly throughout, giving them less rotational inertia. Then we applied tape to make sure they were stabilized. One thing about the disks is that they are very light so alone on the axle they were not very stable, but two great minds such as Paul and I were able to fix that. We chose to put four wheels mainly just for stability. We started off with three wheels, but the car leaned to the slide and we realized that this would not be our fastest design. After we put four wheels the car stayed level and achieved greater speed. The wheels were also fairly large because the larger wheels can cover more distance in less time, and since this lab is all about time that was the best idea.

               The conservation of energy applies to our car, because when the lever-arm generates the force on the axle the energy conserved and is transferred to the wheels. The law of conservation of energy states that energy cannot be destroyed, and must be transferred to something no matter what. So we had to make sure that the energy was being transferred in a way that would be beneficial to our car. Applying duct tape to the axle in order to keep it in place, preventing friction from robbing us of some of our energy. In order to get the most velocity, we needed to generate as much kinetic energy as possible. Because since our car had a very low mass it would have to have a large velocity in order to get a lot of kinetic energy.

              Our lever arm was about eighteen inches long. We knew from our study of torque that we could generate more torque with a longer lever arm. Because, torque=force x lever arm, so we left the force the same (the force the mouse trap generated) and we just made a lever arm that was considerably larger than our opponents. This made the torque on the axle greater, causing it to rotate faster, and in turn the wheels spun faster, giving us more speed. We were able to do more work over a period of time, in other words generate more power due to our long lever arm.

         As far as rotational inertia goes we used disks so that our rotational inertia would be less. The mass of the disks is evenly distributed so that results in a lesser rotational inertia. Because they were larger in comparison to the others wheels they were able to cover more distance less time. Due to the greater tangential velocity, which was caused by the fact that the outside of the wheels had to spin faster in order to keep up with the center. The rotational velocity directly relates to how fast the axle is rotating. So, by generating a large amount of torque with our lever arm we were able to generate a lot of rotational velocity.

         We can’t calculate the amount of work the spring does because we do not know how to figure out how much force the spring generated (work = force x distance). Also the spring constantly changes position, and it moves so quickly that we would not be able to calculate the height at which it had potential energy; therefore we could not find the potential energy (mass x height). I believe that we could calculate the kinetic energy if we had a way to measure the speed of the spring. However, we don’t, so we cannot find the kinetic energy either.

         When we made our original design we really did not know what we were doing. As a result, our final design was a very upgraded version of our original design. Originally we were just going to use the mousetrap as the lever arm, but that changed because we needed more torque. Then we had to find ways to secure the wheels better, so that the wheels would not steal energy from the car (I explained how we did this in the first and second paragraphs). Some of the problems were wheel stabilization, generating enough force to get our car moving at blazing speeds, and reducing friction, all of which we were able to fix as I explained already. If I had a redo I would most likely try to find a more rigid lever arm, because ours bent which took some of the energy. If we could find one that didn’t bend I feel like that would have increased our speed exponentially. Also, we could have possibly found a better way than duct tape to stabilize the wheels. However, we came out victorious, so thought these changes would have been nice for more personal satisfaction, they were not needed to thrash the competition.

         

Mousetrap Car Construct Day One

On the first day of construction, Paul and I were not able to do very much because we did not have all of the necessary supplies needed. However, we did make some progress. We took our mousetrap and drilled two holes on each end, so we could insert screw holders. These will be used to attach an axle to the mousetrap. One of our main challenges was to find a way to keep the axle from sliding back and forth, because we knew this would decrease the speed we would be able to achieve. Sliding back and forth would create unnecessary friction, resulting in a loss of energy. To stop this we applied duct tape near the screw holders that prevented the axle from sliding, but at the same time did not hinder the spinning of it. We then tested the power that we could generate with our trap attached to the axle. We tinkered with many different ways of attaching a string to the mousetrap and the axle. Should we just wrap it, tape it then wrap it, secure it near the wheels or in the middle of the axle? Finally we came to the conclusion that taping then wrapping it in the middle of the axle would be the best choice. Then we let the trap go to see how many rotations we could get. It turns out that the mousetrap actually generates enough power to possibly do what we are trying to without adding a lever-arm, which is to have the fastest time in five meters. However, we still plan on adding a lever-arm, due to the fact that the more power the better. We are trying to blow the competition away! Next construction day we plan on attaching the wheels and the base.

Mousetrap Car with Paul

Paul and I came up with the concept for our mousetrap car after watching many videos on youtube. Many people claimed to have the best mousetrap cars, but we used our knowledge of physics to help us figure out which one we thought we needed to use. The part that was the deciding factor was actually what type of wheels the cars used. Some had holes in them, some were big, and some were small. Knowing what we know about rotational inertia, we knew we had to use a solid wheel.

The wheels will have rubber bands wrapped around them in order to achieve more friction, so that they will grip the floor. Which means that when the mouse trap gets the wheels rotating they won't do any excess spinning without moving. One of our main points of emphasis was to make everything as simple as possible, so that we could reduce the amount of error possible. We are planning on using the normal lever-arm of the mousetrap. Also we are going to use smaller wheels on the front of the car to reduce the mass and create less rotational inertia. Since this race is about speed and not distance, we must be able to achieve as much acceleration as possible, which is why we are using things like the rubber bands and smaller wheels

Materials
Materials provided by Mrs. Lawrence
Rubber Bands -- Goes on the wheels
Paint Sticks -- Used to put wheels on
Kebab Stick -- Axis of the car

Unit 5 Blog Reflection

Unit 5 was all about rotational motion. We covered concepts from tangential speed to conservation of angular momentum. Thats a lot of information, but I'm going to do my best to explain it all. Let's start off with tangential speed, which is the linear speed tangent to a curved path. The "v" in this image shows tangential velocity. Tangential speed ~ radial distance x rotational speed.

Tangential speed is related to something called, rotational speed. Which is the number of rotations or revolutions per unit of time. A real life example, is a merry-go-round. Pretend there is one kid sitting very close to the center, then there is another sitting on the edge. They both are moving with the same rotational speed, because they are sitting on the same object that is making a certain amount of rotations per unit of time. However, the kid sitting near the edge of the merry-go-round has a faster tangential speed, due to the fact that he is further away from the center, thus his radial distance is greater.That leads me into my next topic off rotational inertia. Which is that property of an object that measures its resistance to any change in its state of rotation: if at rest, the body tends to remain at rest; if rotating, it tends to remain rotating and will tend to do so unless acted upon by an external torque. An example of rotational inertia is a circus tightrope walker. Most of the mass of the pole is located away form the axis of rotation, giving it more rotational inertia. If the tightrope walker begins to fall over the pole will resist this change in rotation, giving the walker more time to correct themselves. The longer the pole the better.

  

In the definition of rotational inertia, I used something called torque. The product of force and lever-arm distance, which tends to produce rotation. 

TORQUE=LEVER-ARMXFORCE

You can have counter and counter clockwise torques, which when equal cause an object to be balanced.

Next we have center of mass and center of gravity. Center of mass is the average postition of the mass of an object. The CM moves as if all the external forces acted at this point. CG id the average postion of weight or the single pooin associated with an object where the force of gravity can be considered to act. If ones center of mass is not within his bass, this will cause that person to lose there balance and fall. This relates back to counter and clockwise torques which must be equal to have balance as I stated earlier. There is two new forces we learned about as well, and they are centripetal force and centrifugal force (doesn't actually exist). Centripetal force is directed towards a fixed point and cause rotation by pulling an object inward. For example if you have a ball on the end of a string and you spin it above your head you are creating centripetal force. Centrifugal force is the outward force you or an object experiences when rotating. When you turn in a car, your body hits the door, this is "centrifugal force" even though there's not even any force acting on you. Centrifugal force is an imaginary force. Angular momentum is the product of a body's inertial and rotational velocity about a particular axis. One thing that must be remembered is that angular momentum is conserved. The formula for angular momentum is ROTATIONAL INERTIA X ROTATIONAL VELOCITY. The concepts in this unit were not very difficult, however there were a lot of new concepts to learn. One thing that was hard to understand at first was the tangential speed and rotational speed and when they remain the same. All of these concepts relate to real life, from on the playground to when you are driving in a car. 

Finding the Mass of a Meter Stick without using a Scale

In order to find the mass of the meter stick without using a scale, I was forced to use my knowledge of physics in order to come up with an answer. First, I figured that I had to balance the meter stick on the edge of the table in order to find its center of mass. Which means that on either side of the center of mass the torques are equal. Then I had to place the weight on one end, which had a mass of 100 grams, and adjust the meter stick to once again find the center of mass. Since I could look on the meter stick and see how long each lever-arm was and i knew the force being applied to the one side I could set up this equation, lever-arm x force = lever-arm x force. I know I can do this because the torques are equal. After I came up with an idea of how to do this I put my thoughts into action. In Step 2 I began by finding the center of mass of the meter stick by balancing it on the edge of the table. The center of mass was at 50.5 cm. Then I placed the 100 gram weight on one side, and then adjusted the meter stick in order to find the new center of mass, which was at 70 cm. The first time I did this process I made a simple mistake. When finding the distance of the lever-arm with the weight, I counted from the center of mass to the end of the stick on the long side. However, all I needed to do was go from the new center of mass to the old center of mass. Which would make the lever-arm of the unweighted side 20 cm instead of 70 cm. This made a huge difference in my calculations. So, after I figured out my mistake the equation looked like (20xforce=30x9.8). The 20 comes from the process I explained above, and the 30 comes from the second center of mass to the end of the stick (weighted side), these are the two lever-arms for the equation. Finally, I got the 9.8 by finding the weight of the 100 gram weight by using the equation w=mg, and this is the force for the weighted side so all that is left to do is find the force on the unweighted side and convert it back to grams. After I completed all of the calculations, I found that the weight of the meter stick to be 150 grams. The actual weight was 149.3, so I was only 0.7 grams off.