Question

A wheel makes half a rotation on a plane surface. If radius of this wheel is 21 cm, what is the displacement of the point touching the ground?​

Answer 1

displacement=perimeter of circle=2πr

d=2X22/7X21

d=132cm

since half rotation is made by the wheel so displacement by the point =132/2=66cm

Answer 2

Explanation:

$\rm displacement \\ \begin{aligned} \\ & = \frac{1}{2} \times \sf circumference \\ \\ & = \frac{1}{2} \times 2\pi \sf r \\ \\ & = \frac{1}{ \cancel{2}} \times \cancel{2} \times \frac{22}{7} \times 21 \: cm \\ \\ & = \frac{22 \times \cancel{21} \ {}^{3} }{ _{1} \: \cancel{7}} \: cm \\ \\ & = \bf66 \: cm \end{aligned}$