An action figure is placed on a toy car which is initially at rest. Then the act

Question

An action figure is placed on a toy car which is initially at rest. Then the action figure moves through 4 time intervals: 1) the car is pushed until it hits a wall, 2) then the action fiqure slides down a ramp, 3) flies off of the ramp and hits a wall at the peak of its trajectory momentarily coming to a complete stop, and finally 4) falling into the toybox and coming to rest. Assume that all surfaces except the wall have non-zero coefficients of static and kinetic friction. For each time interval, including the endpoints, determine whether the total work done on the action figure by gravity (g), normal forces (N), and friction (f) is positive, negative, or zero. Neglect drag. v=0 toys | |v=0 Replay

Explanation / Answer

We know W=F.d=Fdcos heta

It means the dot product of force and displacement

1)For 1st time interwal

Since the direction of displacement is in +x axis and the force due to gravity and normal force are in vertical direction making an angle of 90 and cos90=0

Thus work done by gravity and due to normal force=0 N

The work done by friction is there when it strikes the wall the friction force and displacement both will act in same direction so it is greater than zero.

2)In the second figure, the work done by gravity is positive as both displacement and gravity make non-zero angle between them which is less than 90.One component of gravity is in direction of motion.

Work done by normal force is zero as there is no displacement in the direction of normal force.

Work done by fiction force is negative as the displacement is opposite to the direction of force.

3)In the third interval since the toy car flies in air so there is no contact so, no normal and friction force acts, thus, work done by normal and friction force will be zero.

There will be the only force due to gravity and it will be postive as displacement and force act in sma edirection.

4)Here work done by gravity is positive as both displacement and force are in same(downward) direction.

Also the work done by normal force will be positive as there is displacement in the direction of normal force(toward left).

There is no friction force so work done by friction force=0

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