A simple spring has length $$l$$ and force constant $$K$$. It is cut in to two springs of length $$l_1$$ and $$l_2$$ such that $$l_1=n l_2$$($$n$$ is an integer). The force constant of spring of length $$l_1$$ is
A particle of mass '$$m$$' moving east ward with a speed '$$v$$' collides with another particle of same mass moving north-ward with same speed '$$v$$'. The two particles coalesce after collision. The new particle of mass '$$2 \mathrm{~m}$$' will move in north east direction with a speed (in $$\mathrm{m} / \mathrm{s}$$ )
A ball kept at $$20 \mathrm{~m}$$ height falls freely in vertically downward direction and hits the ground. The coefficient of restitution is 0.4. Velocity of the ball first rebound is $$\left[\mathrm{g}=10 \mathrm{~ms}^{-2}\right]$$
A mass '$$\mathrm{M}$$' moving with velocity '$$\mathrm{V}$$' along $$\mathrm{X}$$-axis collides and sticks to another mass $$2 \mathrm{M}$$ which is moving along $$\mathrm{Y}$$-axis with velocity '$$3 \mathrm{~V}$$'. The velocity of the combination after collision is