Question

A particle moves in circular path of radius 1m with uniform speed and takes 4 sec to complete the circular path. Find distance, displacement and average speed for
i) one Complete rotation
ii) half rotation

Answer 1

After a complete rotation:
since displacement is a vector quantity it depends only on initial and final position
for a complete rotation displacement will be zero since initial and final positions are same

distance being scalar quantity is equal to the circumference of the circle
=2(pi)r
=6.28m

Speed again being a scalar quantity can be given by distance travelled upon total time taken
=6.28÷4
=1.57m/s


for a half rotation :
displacement being a vector quantity will be given by the diameter of the circle since they make the initial and final positions
=2r
=2m

distance can be given by half the circumference of the circle for it is a scalar quantity
=(pi)r
=3.14m

Speed will be again given by distance travelled upon time taken
=3.14÷2
=1.57m/s
(NOTE:4s for full rotation...so 2s for half rotation)