Question

An athlete completes one round of a circular track of a diameter of $200m$ in $40s$ What will be the displacement at the end of $2minutes40s$?

• A. $2200m$
• B. $220m$
• C. $22m$
• D. zero

Answer 1

The correct option is D

zero

Step 1: Given data

1. Diameter of circular track $d=200m$
2. Radius $r=\frac{200}{2}=100m$
3. Time is taken by the athlete to complete one round of circular track $t=40seconds$
4. Now, time $T=2min40s=(2\times 60)+40=160seconds(\sin ce,1min=60sec)$

Step 2: Definition

1. Displacement is measured by the shortest distance between the initial and final positions.
2. If the initial and final point is the same as a moving body then the displacement of the object is zero

Step 3: Calculating displacement.

1. The number of rounds covered by the athlete $N=\frac{Totaltime}{Timetakentocompleteoneround}$ $\frac{T}{t}=\frac{160}{40}=4$
2. Here the athlete completes 4 rounds of the circular track. So total displacement is zero. Because the initial and final point is the same of the athlete.

Thus, the displacement at the end of $2minutes40sis$ Zero.