question_answer

(i) State Newton's first law of motion. (ii) A scooter is moving with an initial velocity of 90 km/h and takes 10 s to stop it, after applying brakes. Calculate the force exerted by the brakes on the scooter if its mass along with the rider is 200 kg. Again what would be the force if the mass is halved? OR (i) State Newton's third law of motion with example. (ii) A revolver of mass 500 g, fires a bullet of mass 10 g with a speed of 100 m/s. Find. (a) Momentum of the bullet. (b) Initial momentum of 'revolver and bullet' as a system. (c) Recoil velocity of the revolver.  

Answer:

(i) Everybody in the universe stays in a state of rest or of uniform motion along a straight line until an unbalanced external force acts on it to change its state.                (2) (ii)                      (1) Force,                                                     (1) Or To every action there is an equal and opposite reaction, e.g., when we exert a force (action) on a wall by pushing it with the palm of our hand, wall also exerts a force (reaction) on our palm.              (1) (ii) (a)              (1) (b) Initial momentum of the system = momentum of the bullet (As the momentum is conserved).     (1) (c) Recoil velocity of the revolver V= ? Initial momentum = Final momentum                                  (2)