An athelete completes one round of a circular track of radius `R` in 40 seconds. What will be the displacement at the end of ` 2 min. 20 second ?

Options

A. Zero
B. 2R
C. `2 piR`
D. `7 piR`

Answer

B

Explanation

Total time of motion on circular track `=2 xx 60 + 20 = 140 s`
Time period of revolution = 40 s Therefore displacement in time `(= 3xx 40 = 120s) = 40 s` zero as athelete will be reaching at the starting point.
Thus displacement in 140 seconds = displacement in second = 2R.