A ball of 0.5 kg collided with wall at 30° with the normal at the point of contact with the wall and bounced back elastically. The speed of ball was 12ms-1. The contact remained for Is. What is the force applied by wall on ball? [JIPMER 2018]

Given, m=0.5 kg, v = 12 ms-1, ∆t = 1s and θ=30°Force applied by wall on ball,             F=∆p∆t or F=pfH-piHΔt∵  In this elastic collision, final and initial velocities will be same but direction changes          (pf)H = mv cosθand    (pi)H = -mv cosθ∴          F=mvcosθ+mvcosθΔt=2mvcosθΔt                F=2×0.5×12×cos30°1=63 N