$A$ girl of mass $40\, kg$ climbs a rope $6\, m$ long at a constant speed in $15$ seconds. What power does she expend during the climb (in $W$)?

Which would have a greater effect on the kinetic energy of an object - doubling the mass,or doubling the velocity?

$A$ light and a heavy object have the same momentum. Find out the ratio of their kinetic energies. Which one has a larger kinetic energy?

$(a)$ State the law of conservation of energy. Explain it with one example.
$(b)$ Two girls,each of weight $400 \, N$,climb up a rope to a height of $8 \, m$. Girl $A$ takes $20 \, s$ while Girl $B$ takes $50 \, s$ to accomplish the task. What is the power expended by each girl?
$(c)$ An electric heater is rated $1500 \, W$. How much energy does it use in $10 \, h$?

Identify the energy possessed by a rolling stone.

State whether the following statement is true or false:
The unit of work is watt.