+1 vote
in Machine Dynamics by (34.3k points)
The combined mass of bicycle and rider is 100 kg, they are travelling at the speed of 16 km/h on a level road. Diameter of rear wheel is 0.9m. The pressure applied on the brake is 100 N and μ = 0.05., find the no. of revolutions made by the bicycle before it comes to rest.

(a) 35

(b) 140

(c) 70

(d) 84

I got this question in class test.

The question is from Brakes topic in chapter Brakes and Dynamometers of Machine Dynamics

1 Answer

0 votes
by (38.6k points)
The correct choice is (c) 70

The explanation is: Ft = μ.Rn = 0.05×100 = 5N

Let x be the distance travelled by the bicycle before coming to rest.

then

Ft.x = mv^2/2

x = 100×4.44^2/(2x 5)

= 197.2m

The distance travelled by the bicycle before coming to rest is 197.2m

now, If N is the no. of revolutions then:

197.2 = πDN

197.2/πx0.9 = N

N = 70.

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