The Newton’s second law of motion states that,

F = m× a

⇒ a = F / m

Where,

F is the force on the body,

m is the mass of the body and

a is the acceleration of the body.

Given,

F = -50 N

The negative sign is because the force applied to the body is retarding and acts in the opposite direction to the motion of the body.

m= 20 kg

Thus, the acceleration is

The first equation of motion at time t, can be written as,

v = u + at

where,

v is the final velocity,

u is the initial velocity,

a is the acceleration of the body.

For the body to stop the final velocity must be equal to zero, thus the equation becomes,

Ans: the total time taken by the body to come to rest is 6 seconds.