Question

A wheel of acar of radius is 21cm is rotating at 600rpm.what s the speed of car at km/hr.

Answer 1

Given, r=21cm

Distance covered in one rotation = 2 * pi * r

                                                      = 2 * 3.14 * 21

                                                     = 131.88cm

Given, RPM =600

Distance covered in a minute = 600 * 131.88

                                                 = 791.28m/min

Speed of car at km/hr = (791.28/1000)/(1/60)

                                     = 47.5 kmph


Hope this helps!

Answer 2

600 rpm means..... 600 complete rounds per minute.

Tht means, per hour it takes 60 x 600 = 36000 rounds

The radius of the wheel (circle) is 21 cm

The circumference = 2*pi*r = 2 * 22/7 *21 = 132 cm

In one rotation it covers a distance equal to its circumference. i.e., 132 cm

In one hour, it takes 36000 rotations.

Distance covered in one hour = 36000 * 132 = 4752000 cm = 47520 m = 47.52 km

The speed of the car is 47.52 km/hr