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.
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