Question

A constant retarding force of50 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?

Options

• 6 s

• 2.5 s

• 15 s

• 50 s

Answer 1

15 s

Explanation:

Given retarding force F = - 50 N,

m = 20 kg, 4 = 15 m/s

v = 0 m/s, t = ?

F = Ma = `("m"("v" - "u"))/"t"`

`therefore "t" = ("m"("v - u"))/"F"`

`= (20(0 - 15))/(- 50)`

= 6 s