Example 1: A car starting from rest moves with acceleration of 2 ms-2 its velocity reach at 20 ms-1 . How long time does the car take part in acceleration activity?

Solution

Here,

initial velocity u = 0

final velocity v = 20 ms-1

acceleration a = 2 ms-2

time = ?

We know.

v = u + at

or, at = v — u

t = (v – u) / a

= (20 ms-1 – 0) / 2 ms-2 =10 s

Ans : l0 s

 

Example 2:

A car starting from rest in straight moves with uniform acceleration of 10 ms-2. What will be the velocity while crossing a person at a distance 80 m ?

Solution

Here,

Initial velocity u = 0

Acceleration a = 10 ms-2

Traveled distance s = 80 m

Final velocity v = ?

We know

V2 = u2 + 2as

So, 0 + 2 x l0 ms-2 x 80 m

= 1600 m2 s2

taking root both the sides, v = 40 ms-1

Ans : 40 ms-1