Question

A uniform force of 4 N acts on a body of mass
40 kg for a distance of 2 metre. The kinetic
energy acquired by the body is

a)320 joule. b)8joule. c)800joule. d)460 joule​

Answer 1

Answer:

(b) 8J

Explanation:

F=4N

m=40kg

S=2m

K.E.=work done = F×S = 4×2 = 8J

Answer 2

The kinetic energy acquired by the body is 8 joules. (option b)

Given,

A uniform force = 4 N,

this force acts on a body of mass = 40 kg,

distance = 2 m.

To find,

The kinetic energy acquired.

Solution,

It can be seen that here, the force acting on the body of mass 40 kg is 4 N.

Now, firstly we need to find the acceleration of the body. This can be done as follows.

From Newton's second law of motion,

$F=ma$     ...(1)

Where

m = mass of the body,

$a$ = acceleration of the body.

Substituting the given values in (1),

$4=40a$

Rearranging and simplifying, we get,

$a=0.1$ m/s².

As we know, from the third equation of motion,

$v^{2} =u^{2} +2as$

$\implies v^{2}=0+2(0.1)(2)$     [∵ u = 0, and s = 2 m]

⇒ $v^{2}$ = 0.4 m/s     ...(2)

Since Kinetic energy is given as,

$KE=\frac{1}{2} mv^{2}$

Using (2), we get,

$KE=\frac{1}{2} \times (40) \times (0.4)$

$\implies KE=20 \times 0.4$

$\implies KE=8J$

⇒ Kinetic Energy = 8 joules.

Therefore, the kinetic energy acquired by the body is 8 joules. (option b)

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