Question

The reflection surface of a plane mirror is vertical. A particle is projected in a vertical plane which is also perpendicular to the mirror. The initial velocity of the particle is 10 m/s and the angle of projection is ${60}^0$. The point of projection is at a distance 5m from particle moves towards the mirror . just before the particle touches the mirror. the velocity of approve of the particle and the image is :

• A. 10 m/s
• B. 5 m/s
• C. $10\sqrt{3}$ m/s
• D. $5\sqrt{3}$ m/s

Answer 1

Answer: (A)

10 m/s

Horizontal component of the velocity is $10cos\left(60\right)=5$

And vertical component is $10sin\left(60\right)=8.66$

The participial will touch the mirror after $=\frac{5}{5}=1s$

In this time vertical velocity will be $V=u-gt=8.66-9.8\times 1=-1.14$

Now the relative velocity will be due to horizontal component of the particle .

Since the vertical velocity will be same .

So, te relative velocity of the particle is $2\times 5=10m/s$.