Work Energy Theorem

Q. Two baseballs are fired into a pile of hay. If one has twice the speed of the other, how much farther does the faster baseball penetrate? (Assume that the force of the haystack on the baseballs is constant).

1. Four times as far
2. Two times as far
3. Same as the first one.
4. Eight times as far

Q. A 1 kg block collides with a horizontal light spring of force constant 2 N/m. The block compresses the spring m from rest position. Assuming that the coefficient of kinetic friction between the block and the horizontal surface is 0.25. What was the speed of the block at the instant of collision?

1. 10 m/s.
2. 7.2 m/s
3. 6.7 m/s
4. 7.9 m/s

Q. A body is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to

1. t^1/2
2. t^3/4
3. t^3/2
4. t²

Q. The bob of a simple pendulum (mass m and length l) dropped from a horizontal position strikes a block of the same mass elastically placed on a horizontal frictionless table. The K.E. of the block will be

1. mgl/2
2. mgl
3. 0
4. 2 mgl

Q.

A 50 g bullet moving with velocity 10 m/s strikes a block of mass 950 g at rest and gets embedded in it. The loss in kinetic energy will be

1. 95%

2. 100%

3. 5%

4. 50%

Q.

The kinetic energy acquired by a mass m in travelling a certain distance d starting from rest under the action of a constant force is directly proportional to

1. Independent of m

2. 

3. m

4. 

Q.

The kinetic energy acquired by a mass m in travelling a certain distance d, starting from rest, under the action of a force F such that the force F is directly proportional to t is

1. Directly proportional to t⁴

2. Directly proportional to t

3. Directly proportional to t²

4. Independent of t

Q.

A body of mass 5 kg is moving with a momentum of 10 kg-m/s.A force of 0.2 N acts on it in the direction of motion of the body for 10 seconds. The increase in its kinetic energy is

1. 2.8 J

2. 3.2 J

3. 3.8 J

4. 4.4 J

Q. Work done by gravity when an object falls a height 'h' is given by

1. 0.5mgh
2. mg
3. mgh
4. gh

Q.

A body dropped from a height H reaches the ground with a speed of 1.2 $\sqrt{gH}$.Calculate the work doneby air-friction.

1. -0.72 mgH

2. - 0.28 mgH

3. -0.72 mgH

4. 1.2 mgH