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A box of mass 11.5kg rests on the flat floor of a truck. The coefficients of fri

ID: 2183517 • Letter: A

Question

A box of mass 11.5kg rests on the flat floor of a truck. The coefficients of friction between the box and floor are us = 0.180 and uk = 0.150. The truck stops at a stop sign and then starts to move with an acceleration of 2.17m/s^2.

a) If the box is a distance 1.85m from the rear of the truck when the truck starts, how much time elapses before the box falls off the truck? Take the free fall acceleration to be g = 9.80m/s^2.

b) How far does the truck travel in this time? Take the free fall acceleration to be g = 9.80m/s^2.

Explanation / Answer

force on the block=pseudo force(ma) - friction(umg) =11.5*2.17-.15*11.5*9.8 [ moving, so uk] so acc=.7 m/s^2 so 1.85=.5*.7*t^2 a)so t=2.3 s b)s'=.5*2.17*t^2=5.7 m