A cyclist starts from the centre O of a circular park of radius 1km, reaches the edge P of the park, then cycles along the PQ cicumference and returns to the centre along OQ as shown in fig. If the round trip taken ten minute, the net displacement and average speed of the cylists (in kilometer and kinetic per hour) is

Options

A. o,1
B. `(pi+4)/(2) ,o`
C. `21.4 , (pi+4)/(2)`
D. o,21.4

Answer

D

Explanation

Net displacement = 0
Total displacement = 0
Total distance PQQO
`=1 + (2pi xx 1)/(4) + 1 = (14.28)/(4)`
Average speed ` = (14.28)/(4 xx 10/60) = (6 xx 14.28)/(4) = 21.42 km//hr`