Question

Are the following true or false? Please explain why.

1. an object undergoing projectile motion always has kinetic energy.

2. A static friction force always oppose the direction of motion of the body that it acts on.

3. When a body is moving in uniform circular motion, it has a constant kinetic energy.

4. Energy is neither created, nor destroyed, it is only transformed; unless a non-conservative force acts on the body.

5. A body with mass always experiences a weight force.

Answer 1

1. False, at a particular height it have a potential energy=mgh.

2. True, static friction always oppose the body's motion in which direction it is tending to move. Static Friction always acts on a body which is in rest.

3. True, because kinetic energy depends on square of velocity which will not change with direction of velocity.

4. True, because non conservative forces like frictional forces doesn't follow the conservation principle.

5. False , it's not true that body always experiences a weight force sometimes net force on body is zero like in lift and in space in that case body feels weightlessness or even feel a zero weight.