Two particles of the same mass are moving in circular orbits because of force, given by $F(r) = \frac{{ – 16}}{r}\, – \,{r^3}$ The first particle is at a distance $r = 1,$  and the second, at $r = 4.$  The best estimate for the ratio of kinetic energies of the first and the second particle is closest to

The kinetic energy acquired by a mass $m$ in travelling a certain distance $d$ starting from rest under the action of a constant force is directly proportional to

The machine as shown has $2$ rods of length $1\, m$ connected by a pivot at the top. The end of one rod is connected to the floor by a stationary pivot and the end of the other rod has a roller that rolls along the floor  in a slot As the roller goes back and forth, a $2\, kg$ weight moves up and down. If the roller is moving towards right at a constant speed, the weight moves up with a

A particle $A$ is projected vertically upwards. Another particle $B$ is projected at an angle of $45^{\circ}$. Both reach the same height. The ratio of the initial kinetic energy of $A$ to that of $B$ is