A suitcase of mass 16 kg is placed on a ramp inclined at 15 ° to the horizontal. The coefficient of friction between the suitcase and the ramp is 0.4. Determine whether the suitcase rests in equilibrium on the ramp, and state the magnitude of the frictional force acting on the suitcase.
Net F =ma
The Attempt at a Solution
The answer is the suitcase is not in equilibrium. But I'm not sure if my working is right to show it is not in equilibrium. This is what I did:
Resolve forces parallel to the ramp:
16gsin 15° - μR= ma
16gsin15° - μ (mgcos15°) =16a
a= -1.28 ms^-2
So since a≠0 , it is not in equilibrium.
But this kinda don't make sense.. How can frictional force be so large that it could pull the suitcase up? Is my normal reaction force, R=mgcos15° , correct?