State the law of conservation of energy.

Avinash can run with a speed of $8 \, m \, s^{-1}$ against a frictional force of $10 \, N$,and Kapil can move with a speed of $3 \, m \, s^{-1}$ against a frictional force of $25 \, N$. Who is more powerful and why?

The power of a motor pump is $2 \, kW$. How much water per minute can the pump raise to a height of $10 \, m$ (in $kg$)? (Given $g = 10 \, m \, s^{-2}$)

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

An iron sphere of mass $30 \, kg$ has the same diameter as an aluminium sphere whose mass is $10.5 \, kg$. The spheres are dropped simultaneously from a cliff. When they are $10 \, m$ from the ground,they have the same:

State the relation between $kWh$ and joule. Define $1$ watt.