Question

As shown in the figure a body of mass $m$ moving vertically with speed $3m/s$ hits a smooth fixed inclined plane and rebounds with a velocity $v_f$ in the horizontal direction. If angle of incline is $30^{{}^{\circ }}$ , the velocity $v_f$ will be

• A. 3 m/s
• B. $\sqrt{3}\text{ m/s}$
• C. $1/\sqrt{3}\text{ m/s}$
• D. This is not possible

Answer 1

Answer: (B)

Velocity along surface remain same
$3\text{sin }30^{\text{o}}={\text{v}}_{\text{f}}\text{sin }60^{\text{o}}$
$3\times \frac{1}{2}={\text{v}}_{\text{f}}\times \frac{\sqrt{3}}{2}$
${\text{v}}_{\text{f}}=\sqrt{3}\text{ m/s}$