Question

A particle passes through point A and B which are 90 m apart, If takes 6 s to cover this distance with uniform acceleration velocity of particle when it passes through B point is 20 m/s what is particle velocity at point A?

• A. 10 m/s
• B. 30 m/s
• C. 15 m/s
• D. 20 m/s

Answer 1

The correct option is A 10 m/s

Given that,

Distance $s=90m$

Time $t=6s$

Velocity $v=20m/s$

Now, the acceleration is

By using equation of motion

$v=u+at$

$a=\frac{v-u}{t}$

Now, using equation of motion

$v^2=u^2+2as$

$v^2=u^2+2\times \left(\frac{v-u}{t}\right)s$

$20\times 20=u^2+2\times \left(\frac{20-u}{6}\right)\times 90$

$400=u^2-30u+600$

$u^2-30u+200$

Now, $u=10m/s,20m/s$

But since the particle is accelerating its initial and final velocities can't be the same.

So, $u=10m/s$

Hence, the velocity is $10m/s$ of the particle at point $A$