Question

An object travels around a circle of radius 6 m with speed $3\pi m{s}^{-1}$. The distance and displacement after 3 second is

• A. 9π m, 6√2 m
• B. 9π m, 0 m
• C. 12π m, 6√2 m
• D. 12π m, 0 m

Answer 1

The correct option is A

9π m, 6√2 m

Given radius of circle r = 6 m, speed = $3\pi m{s}^{-1}$

Distance travelled = speed $\times$ time = 3$\pi$ $\times$ 3 = 9$\pi$

Circumference of circle = 2$\pi$r = 12$\pi$ m

In 3s it would have travelled $\frac{9\pi }{12\pi }$ = $(\frac{3}{4}{)}^{th}$ of the circle.

Displacement = Shortest distance between initial and final points

= $\sqrt{(6^2+6^2)}$ m

= $6\sqrt{2}$ m