**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

**V ^{2} = u^{2} + 2as**

So, 0 + 2 x l0 ms^{-2} x 80 m

= 1600 m^{2} s^{2}

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

**Ans : 40 ms ^{-1}**