A car of mass 800kg moving at 54 kmh-1

is brought to rest over a
distance of 15m. Find retarding force developed by brakes of car.

Asked by aryan2mumbai | 1st Sep, 2020, 07:49: PM

Expert Answer:

m = 800 kg 
u = 54 km/h = 15 m/s 
v = 0 
s = 15 m 
 
By third equation of motion, 
v2 = u2 + 2as 
0 = 152 + 2 a x 15 
-225 = 30 a 
a  = 225/30 = -7.5 m/s2 
 
F = ma = 800 x (-7.5) = -6000 N 
 
negative sign indicates that the force is retarding due to applying brakes. 

Answered by Shiwani Sawant | 1st Sep, 2020, 11:20: PM