Question

Two cars $A$ and $B$ are moving with a speed of $15$ $ms^{- 1}$ and $5\,ms^{- 1}$ and acceleration of the cars are $1\,ms^{- 2}$ and $6\,ms^{- 2}$ respectively. Then the minimum separation between them is

• A. $5 \, m$
• B. $10 \, m$
• C. Zero
• D. None

Answer 1

Answer: (B)

$v_{A B}=10ms^{- 1},a_{A B}=-5ms^{- 2}$
$s_{A B}=10t-\frac{5}{2}t^{2}$
Minimum displacement of A w.r.t. B
$s_{A B_{\min}}$ is at $t=\frac{10}{5}=2$
Minimum separation $=20-10=10m$