A ball falls under gravity from a height of 10 m with an initial downward velocity u . It loses one third of its energy in collision and then rises back to 5 m . The initial velocity u is $\left(\mathrm{g}=10 \mathrm{~ms}^{-2}\right)$

A scooter moves with a speed of $$7 \mathrm{~ms}^{-1}$$, on a straight road and is stopped by applying the brakes. Before stopping, the scooter travels $$10 \mathrm{~m}$$. If the weight of the scooter is $$\mathrm{W}$$, then the total resistance to the motion of the scooter will be

When water falls from a height of $$80 \mathrm{~m}$$ at the rate of $$20 \mathrm{~kg} \mathrm{~s}^{-1}$$ to operate a turbine the losses due to frictional force are $$20 \%$$ of input energy. How much power is generated by the turbine?