Question

A constant retarding force of 50N is applied to a body of mass 20kg moving initially with a good speed of 15m/s. How long does the body take to stop

Answer 1

“good speed of 15m/s”???

Retardation (a) = F/m
= 50/20
= 2.5 m/s^2

Now, use v = u + at
0 = 15 + (-2.5)t
t = 15/2.5
t = 6 seconds

It takes 6s for body to stop.

Answer 2

Answer:

The body takes 6 seconds to stop.

Explanation:

To answer this question, we'll use the following relationship:

$F=\frac{m(v-u)}{t}$        (1)

Where,

F=force exerted on a mass m body

m=mass of the body

v=final velocity

u=initial velocity

t=total time taken

From the question we have,

The retarding force=50N

Mass of the body(m)=20kg

The initial velocity(u)=15m/s

The final velocity(v)=0       (as the body comes to stop)

By substituting all the required values in equation (1) we get;

$50=\frac{20(0-15)}{t}$

$t=\frac{20\times -15}{50}$

$t=-6$

$|t|=6\ second$       (as time cannot be negative)

Hence, the body takes 6 seconds to stop.

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