Name the practical unit of power in engineering.

When a stone of mass $m$ falls through a vertical height $d$,the decrease in the gravitational potential energy is:

How many watts are there in $1$ horsepower (in $watts$)?

$(i)$ Derive an expression for the kinetic energy of an object. Write the $SI$ unit of kinetic energy.
$(ii)$ An object of mass $10 \, kg$ is moving with a uniform velocity of $5 \, m s^{-1}$. Calculate the kinetic energy possessed by the object.

We wind our watch once a day,what happens to the energy?

$A$ block of mass $5 \,kg$ is lying on a frictionless table. $A$ force of $20 \,N$ is applied on it for $10 \,s$. Calculate its kinetic energy. (in $J$)