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
