Question

wuatis thco eent OI Knetic inctOn 38. (I) Suppose you are standing on a train accelerating at 0.20 g. What minimum coefficient of static friction must exist between your feet and the floor if you are not to slide? 39. (II) The c0efficient of static friction between hard rubber and normal street pavement is about 0.90. On how steep a hill (maximum angle) can you leave a car parked? 40. (II) A flatbed truck is carrying a heavy crate. The coeffi- cient of static friction between the crate and the bed of тв the truck is 0.75, What is the maximum rate at which the driver can decelerate and still avoid having the crate slide against the cab of the truck?

need help with number 40

Answer 1

(40 )-

in this case , force due to deceleration will be equal to frictional force,

ie,

F_a= F_f

m a = u mg , where u is frictional constant

a= u g

a= 0.75 x 9.8 = 7.35 m/s^2

maximum rate = 7.35 m/s^2