# Recent content by rayoub

1. ### Centripetal force on a vehicle while cornering

Think of a football player that is avoiding a defender by making a quick change of direction. He digs in the side of his foot and pushes off in the opposite direction. The force of the shoe on ground compresses some dirt. The force of the ground on the shoe is what pushes him off. The...
2. ### What happens to energy when work is done?

Here is a statement of the work-energy theorem: $$W_{AonB} = K_{B2} - K_{B1} = ΔK_{B}$$ This does not give us the exact energy change of A unless the interaction between A and B is conservative, i.e. elastic. In that case, by the conservation of mechanical energy we have K_{A1} + K_{B1} =...
3. ### Elastic Collision: how do the forces and work done make sense?

I think you answered your own question here. They are both going on at the same time because they are the same thing - part of the same interaction. I remember being confused by this same thing. Hopefully, I hit upon the source of misunderstanding for you. This applies to all action/reaction...
4. ### Elastic Collision: how do the forces and work done make sense?

They are two ways of looking at the same interaction. From the perspective of ball 1 it does positive work on ball 2 and comes to a stop. From the perspective of ball 2 it does negative work on ball 1 until ball 1 comes to a stop. Another way of saying it is that they are an action/reaction...
5. ### Reduction in Apparent weight

Imagine the body standing on a scale. First case: Your body is not accelerating downward. You are in equilibrium. The normal force (n) exerted by the scale is equal and opposite to the weight (mg) of the body. Hence, F = ma = n - mg = 0 Second case: The body is accelerating downward in...
6. ### Torque, angular momentum and a fixed axis-of-symmetry requirement

I'm reading through "University Physics 14th edition" by Young and Freeman. Section 10.5 on angular momentum for a rigid body around a fixed axis of rotation is derived as L = Iω. However, it shows that this is only the case for the fixed axis of rotation being an axis of symmetry. In section...