Question

A man runs towards a stationary mirror at a speed of $15m/s$. What is the speed of his image with respect to the mirror?

• A. $7.5m/s$
• B. $15m/s$
• C. $30m/s$
• D. $45m/s$

Answer 1

The correct option is C $30m/s$

As $\left|u\right|=\left|v\right|\therefore \left|\frac{du}{dt}\right|\left|\frac{dv}{dt}\right|$

Speed of man=Speed of the image

As mirror is stationary and hence speed of image w.r.t mirror will be $15m/sec$.

It is only when asked with respect to the man, speed of image can be written as$=15m/sec-(-15m/sec)=30m/sec$