Match the column I with column II and select the correct answer by choosing the appropriate option.

Column I	Column II
P. Joule	1. Power
Q. Watt	2. $1 \mathrm{hp}$
R. $1 \mathrm{kW} \mathrm{h}$	3. Energy
S. $746 \mathrm{W}$	4. $3.6\times {10}^6 \mathrm{J}$

An object of mass $10 \mathrm{kg}$ is dropped from a height of $20 \mathrm{m}$. Calculate the potential energy and kinetic energy of the object at various heights as mentioned in the data:

Show by calculations that the above data verifies the law of conservation of energy. (take $\mathrm{g}=10 \mathrm{m}/{\mathrm{s}}^2$ )

Give reason for the following:

Winding the spring of a toy car makes it run on the ground.