A skater of mass $50 \mathrm{kg}$ moves down from $\mathrm{A}$ to $\mathrm{B}$. The frictional forces are absent. What is the kinetic energy at $\mathrm{B}$? (take $\mathrm{g}=10 {\mathrm{ms}}^{-2}$).

Write an expression for the work done when a force is acting on an object in the direction of displacement

Write an expression for work done when force is acting on an object at an angle to displacement.

Define energy. Give it's Sl unit.

Which physical quantity has a unit electron volt ($\mathrm{eV}$)?

Which physical quantity has a unit kilo-watt hour $\left(\mathrm{kWh}\right)$?

Is energy a scalar or a vector quantity? Why?

Define kinetic energy.

What is mechanical energy?