Define external force.

A bomb of mass $3 \mathrm{m} \mathrm{kg}$explodes into two pieces of mass $\mathrm{m} \mathrm{kg}$ and$2\mathrm{m} \mathrm{kg}$. If the velocity of m kg mass is $16 {\mathrm{ms}}^{-1}$, the total kinetic energy released in the explosion is

A bomb of Mass $30 kg$at rest explodes into two pieces of masses $18 kg$ and $12 kg$. The velocity of 18 kg mass is $6 m/s$. The kinetic energy of the other mass is.
 

State law of conservation of momentum and prove it.

A horizontal force $‘F’$is applied to keep the block stationary on a frictionless inclined plane. Find the angle of incline, for which the applied force is equal to the weight of body: 

Give an example of non-contact force.

Define a contact force.

What causes acceleration?

What are balanced and unbalanced forces?

$1 \mathrm{kg} \mathrm{f} =$ _____ $\mathrm{N}$

(Choose from: $98 / 9.8 / 49 / 4.9$)

Define force.