The problem propmpts us with the info:
"Two friends play with a card-board box on a grassy hill side.
The boy in the box has a mass of 50.0 kg and the box has a mass of 5.00 kg.
The incline of the hill is 44° and its height is 10 meter.
Assume that friction plays a negligible role on the hill.
You will need to know the length of the incline."
We need to find the acceleration, velocity at the bottom of the hill, and the friction force in Newtons (this is when friction is no longer negligible. "The box slides horizontally across the grass at the bottom of the incline, coming to a stop 13.1 meters from the base of the incline. Assume friction plays a significant role bringing the box to a stop").
I have the Max=mgsine44-uN, May=n-49cos44=0 by rotating the motion map so acceleration is horizontal. I found n to be equal to 49cos44, 35.2. When I plugged in "n" to the max equation I found u to equal .404. It says friction is negligible, so does that mean u=0? But, if u=0 then you can't find acceleration through a=ug. I used trig to find the length of the incline to be 14.4 m. To find velocity at the bottom of the hill, I made an xvvat chart and used the values initial velocity=0, my found acceleration (which apparently is wrong), and the position, x, as 14.4. My friction should be f=un, but my n must not be correct.