### Class XI

A 1-kg block is lifted vertically 1m by a boy. The work done by the boy is
1. 1 J
2. 0 J
3. 9.8 J
4. 0.1 J
Physically, the notion of potential energy is applicable only to
1. The class of forces where work done against the force gets converted to thermal energy
2. The class of forces where work done against the force gets converted to kinetic energy
3. The class of forces where work done against the force gets stored up as energy.
4. The class of forces where work done against the force gets dissipated
Considering a completely inelastic collision of a particle of mass m1m1 moving with initial velocity v1v1 and a stationary particle of mass m2m2 the final velocity is given by
1. m1 2m1+m2 v1
2. m1 m1+2m2 v1
3. m1 m1+m2 v1
4. m2 m1+m2 v1
A trolley of mass 200 kg moves with a uniform speed of 36 km/h on a frictionless track. A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a speed of 4 m s−1s−1 relative to the trolley in a direction opposite to the its motion, and jumps out of the trolley. How much has the trolley moved from the time the child begins to run ?
1. 27.8 m
2. 25.9 m
3. 24.1 m
4. 23.3 m
A12-pack of Omni-Cola (mass 4.30 kg) is initially at rest on a horizontal floor. It is then pushed in a straight line for 1.20 m by a trained dog that exerts a horizontal force with magnitude 36.0 N. Use the work–energy theorem to find the final speed of the 12-pack if there is no friction between the 12-pack and the floor
1. 4.48 m/s
2. 4.38 m/s
3. 4.68 m/s
4. 4.58 m/s
0
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