7. A 100 g iron ball having velocity 10 m/s collides with a wall at an angle 30° and rebounds with the same angle. If the period of contact between the ball and wall is 0.1 second, then the force experienced by the wall is
(a) 10 N (b) 100 N
(c) 1.0 N (d) 0.1 N
answer : a
(6)