Classes
Class 9Class 10First YearSecond Year
$In which case is more work done? When a 50 \mathrm{~kg} bag of books is lifted through 30 \mathrm{~cm} or when a 50 \mathrm{~kg} create is pushed through 2 \mathrm{~m} across the floor with a force of 50 \mathrm{~N} ?$  $v. The kinetic energy of a body of mass 2 \mathrm{~kg} is 25 \mathrm{~J} . Its speed is(a) 5 \mathrm{~ms}^{-1} (b) 12.5 \mathrm{~ms}^{-1} (c) 25 \mathrm{~ms}^{-1} (d) 50 \mathrm{~ms}^{-1}$  $6.1 A man has pulled a cart through 35 \mathrm{~m} applying a force of 300 \mathrm{~N} . Find the work done by the man.(10500 J)$  $How large a force is required to accelerate an electron \left(\mathrm{m}=9.1 \times 10^{-31} \mathrm{~kg}\right) from rest to a speed of 2.0 \times 10^{7} \mathrm{~ms}^{-1} through a distance of 5.0 \mathrm{~cm} ?$  $6.5 Define energy give two types of mechanical energy.$  $When a rocket re-enters the atmosphere its nose cone becomes very hot. Where does this heat energy come from?$  $What sort of energy is in the following:(b) Water in a high dam$  