**Problem 1:** A force acting on an object varies with distance‘d’ as shown in the figure. Calculate the work done by the force as the object is displaced from d = 0 to d = 6 m?

**Problem 2:** A 70 kg man runs up a long flight of
stairs in 4.0 seconds. The vertical height of the stair is 4.5 m. Calculate his
power.

**Problem 3:** A body of mass 2.0 kg is dropped from a rest position 5.0 m above the ground. What is its velocity at height of 3.0 m above the ground?

**Problem 4:** A man pulls a trolley through a distance of 50 m by applying a force of 100 N which makes an angle of 30 with the horizontal. Calculate the work done by the man.

**Problem 5:** A man whose mass is 70 kg, walks up to the third flour of a building which is 12 m above the ground in 20 seconds. Find his power in watts and horse powers.

**Problem 6:** A ball of mass 100 grams is thrown vertically upward at a speed of 25 m/s. If no energy is lost, determine the height it would reach. If the ball only rises to 25 m, calculate the work done against the air resistance. Also calculate the force of friction.

**Problem 7: **An object of mass 1000 g falls from a height of 30 m on the sand below. If it penetrates 4 cm into the sand, what opposing force is exerted on it by the sand? Neglect air friction.

#### Problem 8: A body of mass m drops from a bridge into water of the river. The bridge is 10 m high from the water surface. (a) Find the speed of the body 5 m above the water surface. (b) Find the speed of the speed of the body before it strikes the water.

**Problem 9:** The JF-Thunder fighter develops a thrust of 3000 N. What horsepower does it at a velocity of 600 m/s.

**Problem 10:** A force of 2000 N is exerted in lifting a 100 kg mass straight up to 10 m.

(a) How much work is done?

(b) What are the K.E and P.E of the object when it gets to that height?