Question

While hauling a log in the back of a flatbed truck, a driver is pulled over by the state police. Although the log cannot roll sideways, the police claim that the log could have slid out the back of the truck when accelerating from rest. The driver claims that the truck could not possibly accelerate at the level needed to achieve such an effect. Regardless, the police write a ticket, and the driver's court date is approaching. The log has a mass of m=859 kg; the truck has a mass of M = 9050 kg. According to the truck manufacturer, the truck can accelerate from 0 to 55 mph in 27.0 s, but this does not account for the additional mass of the log. OIO Calculate the minimum coefficient of static friction His needed to keep the log in the back of the truck. 721 Hg = According to the scientific literature, the coefficient of static friction between the log and the trailer bed should be roughly 0.840. Given this fact, select the most accurate statement. There is little chance the log could have slid out the back. The results are not conclusive. The police officer is correct. The log posed a real danger. Note that state laws typically describe the conditions under which cargo needs to be secured. Violation of these requirements is a civil violation.

Answer 1

To find minimum coefficient of friction, first we find the acceleration

u = 0 m/s

v = 55 mph = 24.5872 m/s

t = 27

so,

a = v - u / t

a = 0.91 m/s²

so,

F = Ma

F = 8241.26 N

with log in truck

a = 8241.26 / ( 9050 + 859)

a = 0.8316 m/s²

so

F = uma

859 * 0.8316 = u * 859 * 9.8

so,

u = 0.085

so,

there is a little chance for slog to slide out !!