Question

A body starts from rest and acquires a velocity 20 m/s in 4 seconds. Find
(i)the acceleration(ii)initial velocity *
O 5m/s^2,zero
O 5m/s,20m/s
24m/s, 4m/s
O 2.5m/s^z,zero​

Answer 1

Working out:

In the question, we are provided with the values and measures of physical quantities involved in Kinematics (Study of motion in physics)

GiveN:

• Starts from rest
• Acquires velocity = 20 m/s
• Time taken = 4 seconds.

To find Accleration and the initial velocity....?

This can be done by using the three equations of motion which are:

• v = u + at
• s = ut + 1/2 at²
• v² = u² + 2as

So, let's solve by using these equations,

By using first equation of motion,

• v = 20 m/s
• u = 0 m/s (Initially at rest)
• t = 4 s

⇛ v = u + at

Plug in the given values,

⇛ 20 = 0 + a(4)

⇛ 4a = 20

⇛ a = 5 m/s²

Initially the body was at rest, hence the initial velocity (u) of the body is 0 m/s.

Hence, acceleration and initial velocity of the body:

$\Large{ \boxed{ \red{ \sf{5 \: m {s}^{ - 2} and \: zero \: (A)}}}}$

And we are done !!

Answer 2

Given:-

Initial velocity = 0 m/s

[Answer of (II); it is 0 m/s because object in rest position have a velocity of 0. This is because they don't change their position with respect to time or no change is visible in their Direction either.]

Final velocity = 20 m/s

Time it took to achieve 20 m/s = 4 s

To Find:-

(I) Acceleration (II) Initial velocity

(I) Acceleration:-

We know,

Acceleration (denoted by 'a') = $\frac{v-u}{t}$

[where, v, u are the final and initial velocities respectively and t stands for time taken to achieve the velocity of (v) from (u).]

So acceleration in this case,

$a = \frac{v}{t} = \frac{20 m/s}{4 s}$

$\implies a = 5 m/s^2$