An athlete completes one round of a circular track of radius
R in 40 sec. What will be his displacement at the end of 2
min. 20 sec ?
(a) Zero (b) 2R (c) 21R
(d) 7TR
Answers
Answer: his displacement would be 2R which is the diametre of the circle.
An athlete completes one round of a circular track having radius 'R' in 40 seconds.
We have to find the displacement of the athele at the end of 2 min 20 sec.
Displacement is defined as the shortest path covered between the initial and final points.
First of all convert the given time into seconds. (2 min 20 sec)
= 2 × 60 sec + 20 sec
= (120 + 20) sec
= 140 sec
Athele completes his one round in 40 sec. Then in 140 sec, he completes 3.5 rounds.
As,
40 sec = 1 round
140 sec = (1 × 140)/40 = 3.5 rounds
Therefore, in 3.5 rounds; athlete will be just at the opposite side of the circular track. Means, equal to the diameter of the circular track.
2 × Radius = Diameter
2 × R = Diameter
Therefore, the displacement of the athele at the end of 2 min 20 sec is 2R.
Option b) 2R