A hammer having a mass of 1 kg going with a speed of 6 m/s hits a wall and comes to rest in 0.1 sec. Compute the obstacle force that makes the hammer stop.

Solution:

Mass of Hammer, m = 1 kg
Initial Velocity, u = 6 m/s
Final Velocity, v = 0 m/s
Time Taken, t = 0.1 s
The acceleration is: a = (v – u )/t

a = ( 0 m/s – 6 m/s ) / 0.1 sec

Therefore, a = – 60 m/s²

[-ve sign means retardation]
Thus, the retarding Force, F = ma = 1 × 60 = 60 N