Question

A cubical room is formed with $6$ plane mirror. An insect moves along diagonal of the floor with uniform speed. The velocity of its image in two adjacent walls are $20\sqrt{2}$ cm/s. Then the velocity of image formed by the roof is ;

• A. $20$ cm/sec
• B. $40$ cm/sec
• C. 9 cm/sec
• D. 45 cm/sec

Answer 1

Answer: (B)

$40$ cm/sec

velocity of it's image in two adjacent wall are showing the components of actual velocity and this actual velocity will be shown in roof.

So actual velocity= $\sqrt{{\left(20\sqrt{2}\right)}^2+{\left(20\sqrt{2}\right)}^2}$ =40 cm/sec