Question

A ball moving on a horizontal frictionless plane hits an identical ball at rest with a velocity of $50cm{s}^{-1}$ . If the collision is elastic, calculate the speed imparted to the target ball if the speed of the striking ball after the collision is $30cm{s}^{-1}$

• A. $20cm{s}^{-1}$
• B. $30cm{s}^{-1}$
• C. $40cm{s}^{-1}$
• D. $50cm{s}^{-1}$

Answer 1

Answer: (C)

As the collision is perfectly elastic
Hence $\frac{1}{2}m{u}_1^2+\frac{1}{2}m{u}_2^2=\frac{1}{2}m{v}_1^2+\frac{1}{2}m{v}_2^2$
$\Rightarrow u_1^2+u_2^2=v_1^2+v_2^2$
${\left(0.5\right)}^2+0={\left(0.3\right)}^2+v_2^2$
$v_2=\sqrt{{\left(0.5\right)}^2-{\left(0.3\right)}^2}$
$v_2=40cm{s}^{-1}$