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An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?

Solution: Diameter of a circular track d = 200m 

Time taken by athlete in complete one round of a circular track t = 40 s

Radius of a circular track r = d/2 = 200/2 = 100 m

Distance covered by athlete in one round of a circular track x = circumference of circular track = 2πr = 2 × 3.14 × 100 = 628 m 

Speed = distance covered / time taken = 628 / 40 = 15.7 m/s 

Total time taken = 2 min 20 = 140s

Distance covered by athlete at the end of 2 minutes 20 s is ,

Distance = speed × total time taken = 15.7 m/s × 140s = 2198 m ≈ 2200 m

Displacement in 2 minutes (= 120s) will be zero because the athlete will complete 3 rounds (one round in 40s) and at that time the initial position and final position will be the same. 

But, after the next 20s, the final position of the athlete will be equal to half of the circumference (one complete round in 40s), so the displacement will be equal to the diameter of the circular track, which is 200 m.

Other NCERT questions solution

Question 2:

Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging (a) from A to B and (b) from A to C?

Question 3:

Abdul, while driving to school, computes the average speed for his trip to be 20 km/ h. On his return trip along the same route, there is less traffic and the average speed is 30 km/ h. What is the average speed for Abdul’s trip?

Question 4:

A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of 3.0 m/s² for 8.0 s. How far does the boat travel during this time?

Question 5:

A driver of a car travelling at 52 km/ h applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km/ h in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?

Question 6:

Fig 8.11 Shows the distance-time graph of three objects A, B and C. Study the graph and answer the following questions: (a) Which of the three is travelling the fastest? (b) Are all three ever at the same point on the road? (c) How far has C travelled when B passes A? (d)How far has B travelled by the time it passes C?

कम्प्यूटर क्या है

An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s? An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?

An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s? An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?