Question

an athlete completes one round of a circular track of radius 2.5m in 12 secs . what will be the magnitude of displacement at the end of 54sec

Answer 1

Given : radius of the track , r = 2.5 m   Time taken to complete one revolution = 12 s    ________________________  So, as we know that circumference = 2πr    So, distance travelled in 12s or one revolution = 2 ×3.14 × 2.5 = 15.6 m    And as initial and final point will be same after the completion of the revolution so   Displacement after completing a revolution will be zero (0)     _________________________  Now for time 54 s    We have 54/12 = 4.5    As one complete revolution is done in 12 s    So in 54s there will be 4 complete revolution and one half revolution .     So the athlete will be at a diametrically opposite point from the initial point    So, displacement =  diameter    i.e., displacement = 2r = 2×2.5 = 5.0 m     So, the magnitude of displacement at the end of 54s will be 5 m.

Answer 2

Distance : How much area is covered by an object regardless of its starting or ending position.

Displacement :an object’s change in position considering its starting position and final position.

In the question athelete completles one round of circluar tracks of radius 2.4m in 12 section.

So in 54 seconds he completes = 54/12 =4.5 round.

so after 4 rounds its displacement is zero beacuse Starting and ending postion is same.