Question

A particle P is projected from a point on the surface of smooth inclined plane (see figure). Simultaneously another particle Q is released on the smooth inclined plane from the same position. P and Q collide after $t=4s$. The speed of projection of P is:-

• A. 5 m/s
• B. 10 m/s
• C. 15 m/s
• D. 20 m/s

Answer 1

The correct option is B 10 m/s

Relative velocity of a particle P in the frame of Q changes linearly with time during the flight of P

Acceleration of Particle P and Q along the inclined is same

Acceleration of particle P perpendicular to the incline plane $=10cos60$

$=10\times \frac{1}{2}$

$=5m/se{c}^2$

So,

$\Rightarrow V_P-5\left(2\right)=0$

$\therefore V_P=10m/sec$

Hence speed of projection of P is 10 m/sec.