Wow is there no one to help with physics???
posted by John on .
A crate of oranges weighing 209 N rests on a flatbed truck 2.0 m from the back of the truck. The coefficients of friction between the crate and the bed are μs = 0.41 and μk = 0.20. The truck drives on a straight, level highway at a constant 7.5 m/s.
(a) What is the force of friction acting on the crate?
N
(b) If the truck speeds up with an acceleration of 2.1 m/s2, what is the force of the friction on the crate?
magnitude N
(c) What is the maximum acceleration the truck can have without the crate starting to slide?
m/s2

Please have patience, John. You just posted about 11 minutes before this post.
Remember that we are all volunteers and answer questions when we have spare time.
Here's a clue: A busy physics teacher is more likely to help you if you give us some idea what you do and don't understand about the problem. 
Sorry
Well i am confused i don't know how to set the problem up to solve for! I don't know whether to use both uK and Us or just one of them :/
Thank you 
John  or whatever you call yourself  please keep the same name for all of your posts.

How would you know its all me?

mustatic use when at rest.

Thanks bobpursley

I got the rest bobpursley but for some reason am not getting the right answer for part b which friction=ma but when i put 209(2.1) the answer isnt right