Coefficient Static Friction Problem

[Lebelee]

Hey guys, i attempted this question and got an answer but I'm not sure if i did it right, since it seemed too simple too me.

http://www.physics.ubc.ca/~mattison/Courses/Phys170/p170-ps6.pdf

It is question #4 on the link, and what i did was use kinematics to find acceleration then simply use F=ma to find the Friction force, (Ff) and F=mg to find the upward force (Fn) and then use Mui = Ff/FN

and got an answer around 0.56.

I was wondering if this is too simple or if the speed of the truck has anything to do with this calculation, since i did not take that into consideration since both the speed of the crate and truck were 80kph (22.2m/s)

 

[Doc Al]

Looks like you did it correctly to me. All that matters is the speed of the crate when it hits the ground.

 

[Lebelee]

Thanks Al.