Question
A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 ms–1. How long does the body take to stop?
Solution
Retarding Force, F = - 50 N
Mass of the body, m = 20 kg
Initial velocity of the body, u = 15 m/s
Final velocity of the body, v = 0
Acceleration produced in the body can be calculated as:
F = ma
-50 = 20 x a
a = 
Using the first equation of motion,
v = u + at
Time (t) taken by the body to come to rest can be calculated as,
Therefore,
t = 
