Question

Two balls are thrown from the top of a tower, one straight down with an initial velocity u and the other straight up with same initial velocity u. What is the ratio of their speeds when they hit the ground?

• A. 1 : 2
• B. 2 : 1
• C. 1 : 1
• D. 2 : 3

Answer 1

The correct option is C 1 : 1

From top to bottom

for A

U initial = u v=? a=g s=d

$v_A^2=U^2+2as$
$v_A^2=u^2+2gd$

$v_a=\sqrt{u^2+2gd}$

For B

U initial=u a= -g s= -d v=?

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

$v_B^2=u^2+2gd$

$v_b=\sqrt{u^2+2gd}$

So

$\frac{v_A}{v_B}=\frac{\sqrt{u^2+2gd}}{\sqrt{u^2+2gd}}$ =1

$v_a:v_B::1:1$

Hence (C) is correct answer