Question

A body is moving with uniform velocity of $8m{s}^{-1}$. When the body just crossed another body, the second one starts and moves with uniform acceleration of $4m{s}^{-2}$. The time after which two bodies meet, will be

• A. $2s$
• B. $4s$
• C. $6s$
• D. $8s$

Answer 1

The correct option is B $4s$

$A\to 8m/s$

$B\to 4m/s^2$

Let us observe the motion of A wrt B

So,

$a_{A/B}=-4m/s^2$

$u_{A/B}=8m/s$

For finding the time after they

will meet

Applying $2^{nd}$ $e{q}^n$ of motion

$0=\left(u_{A/B}\right)t$ $t\frac{\left(a_{A/B}\right)}{2}{t}^2$

$\Rightarrow 0=8t-\frac{4}{2}{t}^2$

$t^2=4t$

$t=4$ or $0$

Option $-B$ is correct.