Write the equation of total mechanical energy of a body having mass $m$ and stationary at height $H$.
A rain drop of radius $2\; mm$ falls from a helght of $500 \;m$ above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original hetght, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey ? What is the work done by the resistive force in the entire journey if its speed on reaching the ground is $10\; m s ^{-1} ?$
Two putty balls of equal mass moving with equal velocity in mutually perpendicular directions, stick together after collision. If the balls were initially moving with a velocity of $45\sqrt 2 \,m{s^{ - 1}}$ each, the velocity of their combined mass after collision is .................. $\mathrm{m} / \mathrm{s}^{-1}$
A ball is projected from top of a tower with a velocity of $5\,\, m/s$ at an angle of $53^o$ to horizontal. Its speed when it is at a height of $0.45 \,\,m$ from the point of projection is ........ $m/s$
A bullet of mass $0.02\, kg$ travelling horizontally with velocity $250\, ms^{-1}$ strikes a block of wood of mass $0.23\, kg$ which rests on a rough horizontal surface. After the impact, the block and bullet move together and come to rest after travelling a distance of $40\,m$. The coefficient of sliding friction of the rough surface is $(g = 9.8\, ms^{-2})$
A neutron moving with a speed $'v'$ makes a head on collision with a stationary hydrogen atom in ground state . The minimum kinetic energy of the neutron for which inelastic collision will take place is....$eV$