Question

A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 m/s comes to rest after 2 s. If one wants to keep this body moving on the same surface with a velocity of 4 m/s, the force required is :-
(1) 8 N (2) 4 N (4) 2 N (3) Zero ​

Answer 1

Answer:

A body of mass 2 kg moving on a horizontal surface with an initial velocity of 4 m/s comes to rest after 2 s. If one wants to keep this body moving on the same surface with a velocity of 4 m/s, the force required is $4\ N$

Explanation:

According to the first equation of motion,

$\mathrm{v}=\mathrm{u}+\mathrm{at}$             ...(1)

Where u and v are the initial and final velocity of the object, t is the time taken and a is the acceleration of the body.

from the question,

$\mathrm{u}=4 \mathrm{~m} / \mathrm{s} \quad \mathrm{v}=\mathrm{0} \quad \mathrm{t}=2 \mathrm{sec} \quad \mathrm{a}=\text { ? }$

Putting these values into equation(1),

$\mathrm{0}=\mathrm{4}+(\mathrm{a\times2)}$

$a=-2 \mathrm{~m} / \mathrm{s}^{2}$  

In the question, it is given that,

Mass of the object (m) = $2\ kg$

Using Newton's laws of motion,

$Force (F) = mass(m)\times acceleration (a)$      ...(2)

Substituting values to the above equation,

$F =2 \times 2=4 \mathrm{~N}$

Correct answer is the second option.