Name the instrument used to measure the coefficient of restitution of a material and explain why frictional force is a non-conservative force.

$A$ particle of mass $m$ moving eastward with a speed $v$ collides with another particle of same mass moving northward with same speed $v$. The two particles coalesce after collision. The new particle of mass $2m$ will move in north-east direction with a speed (in $m/s$) of:

If a shell fired from a cannon explodes in mid-air,then which of the following is true?

On complete combustion,a litre of petrol releases heat equivalent to $3 \times 10^7 \, J$. In a test drive,a car weighing $1200 \, kg$ (including the driver) travels $15 \, km$ per litre while moving at a uniform speed on a straight track. Assuming that the friction offered by the road surface and air is uniform,calculate the force of friction acting on the car during the test drive,given that the efficiency of the car engine is $0.5$. (in $, N$)

Consider a one-dimensional collision involving a body of mass $m_1$ moving in the positive $x$ direction with speed $v_0$ and a second body of mass $m_2$ initially at rest. The collision can be completely inelastic,completely elastic,or partially inelastic. After the collision,$m_1$ moves with velocity $v_1$ and $m_2$ moves with velocity $v_2$. Determine the range of final velocity $v_1$ for the following cases:
$(A)$ If $m_1 > m_2$
$(B)$ If $m_1 < m_2$

$A$ block moving horizontally on a smooth surface with a speed of $40 \, m/s$ splits into two equal parts. If one of the parts moves at $60 \, m/s$ in the same direction,then the fractional change in the kinetic energy will be $x: 4$ where $x = ..... .$