Question

In a straight line motion of 50 m the particle moves with constant acceleration. If initial speed is 3 m/s and final speed is 6 m/s, then the average speed is

• A. 4 m/s
• B. 4.5 m/s
• C. 5 m/s
• D. 5.5 m/s

Answer 1

The correct option is B 4.5 m/s

Given,

$u=3m/s$

$v=6m/s$

$s=50m$

From 3rd equation of motion,

$v^2-u^2=2as$

$6^2-3^2=2\times 50a=100a$

$a=\frac{36-9}{100}=\frac{27}{100}=0.27m/s^2$

From 1st equation of motion,

$v=u+at$

$at=v-u$

$t=\frac{v-u}{a}=\frac{6-3}{0.27}=\frac{100}{9}sec$

The average speed, $v_{avg}=\frac{s}{t}$

$v_{avg}=\frac{50}{100/9}=\frac{9}{2}=4.5m/s$

The correct option is B.