How much work should be done on an object of $120 \, kg$ to increase its speed from $25 \, m s^{-1}$ to $40 \, m s^{-1}$ (in $, J$)?

Calculate the kinetic energy of a body of mass $2 \, kg$ moving with a velocity of $0.1 \, m s^{-1}$. (in $, J$)

Define work. Write an expression for work in terms of force and displacement. State the $SI$ unit of work done.

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?

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.

When is the work done by a force said to be negative? Give one situation in which one of the forces acting on the object is doing positive work and the other is doing negative work.