Question

A 90 gm ball moving with 100 cm/s collides with 10 gm. ball at rest. If collision is perfectly elastic, their respective velocities are

• A. 80 cm/s ; 180 cm/s
• B. 180 cm/s ; 80 cm/s
• C. 50 cm/s ; 120 cm/s
• D. 120 cm/s ; 50 cm/s

Answer 1

The correct option is A 80 cm/s ; 180 cm/s

Using momentum conservation
$90\times 100=90v_1+10v_2$................(1)

& $e=\frac{v_2-v_1}{100}=1$

$v_2-v_1=100$...............(2)
from (1) & (2)
$v_1=80cm/s$
$v_2=180cm/s$