Question

A ball is projected vertically up with a velocity of $40$ $m/s$. At the same time another ball is dropped from a height of $100$ m. The magnitudes of their velocities are equal after a time of $(g=10m/s^2)$

• A. 2 sec
• B. 1 sec
• C. 3 sec
• D. 4 sec

Answer 1

Answer: (A)

2 sec

$v_A=40-gt$
$v_B=gt$
$|v_A|=|v_B|$
$\Rightarrow 40-gt=gt$
$t=\frac{40}{2\times 10}=2sec$