Name: Class: Date:SMK (L) Methodist Kuala Lumpur

Physics Form 42.0 Forces and Motion2.10 Work, energy and power

1. What is the work done by a man when he pushes a box with a force of 90 N through a distance of 10 m? State the amount of energy transferred from the man to the force.

2. A sales assistant at a shop transfers 50 tins of milk powder from the floor to the top shelf. Each tin has a mass of 3.0 kg and the height of the top shelf is 1.5 m.(a) Calculate the total work done by the sales assistant.

(b) What is his power if he completes this work in 250 s?

3. Lim rides his bicycle down the slope of a hill 3 m high at an initial velocity of 2 m s-1 without pedalling. At the foot of the hill, the velocity is 6 m s-1. Given that the mass of Lim with his bicycle is 75 kg. Find (a) the initial kinetic energy of the bicycle,

(b) the initial potential energy of the bicycle,

(c) the work done against friction along the slope.

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4. A stone is thrown upward with initial velocity of 20 m s-1. What is the maximum height which can be reached by the stone?

5. A ball is released from point A of height 0.8 m so that it can roll along a curve frictionless track. What is the velocity of the ball when it reaches point B?

6. Figure below show a trainee of mass 56 kg glides down from a platform to the ground. His velocity when reaching on the ground is 12 m s-1.

(a) Calculate the change in gravitational potential energy of the trainee.

(b) What is his kinetic energy when he reaches the ground?

(c) Explain the difference in your answers in (a) and (b)

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