Name the practical unit of power in engineering.

$A$ porter moving vertically upstairs with a load on his head does work. Why?

An object of mass $10 \ kg$ is made to fall freely from a height of $10 \ m$. Complete the table:

Height of object $(m)$	$PE$ $(J)$	$KE$ $(J)$	Mechanical Energy $(J)$
$10$	...	...	...
$8$	...	...	...
$5$	...	...	...
Just above ground	...	...	...

Hence,state the law of conservation of energy.

Explain that a flying bird possesses both potential and kinetic energy and provide their expressions.

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

$A$ ball is dropped from a height of $10\, m$. If the energy of the ball reduces by $40\%$ after striking the ground,how much high can the ball bounce back (in $,m$)? $(g = 10\, m \,s^{-2})$