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Homework Statement
A 5.49 kg block covered in sandpaper is pushed along the ceiling of a room under construction. The block is pushed across the ceiling with a force of 81.6 N directed at an angle of 70.0° to the horizontal. If the coefficient of kinetic friction between the paper and the ceiling is 0.533, what acceleration does the block undergo?
Homework Equations
component forces in x-direction = Fextcos70 - Ff
The Attempt at a Solution
ma = Fextcos70 - uFn
= 81.6cos70 - (0.533)(5.49*9.8)
= 27.9 - 28.7
** so i would get a negative number: that doesn't really make sense. Here I say that the normal force is equal in magnitude to the weight. Is this correct? Or do i need to include the y-component of the push when looking for the normal force?
Help would greatly be appreciated!