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Engineering101

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**Physics Help Greatly Appreciated -- Block sliding down ramp**

A 7.7 kg block is on an incline with a coefficient of static friction of 0.50. The angle that the ramp makes with the horizontal is increased gradually, until the block begins to slide down the ramp. If you know that the coefficient of kinetic friction between the block and the plane is 0.34, find the time it will take the block to slide down the ramp a distance of 0.47 m starting from rest.

Ff=uFn

My solution:

arctan(.5)=angle of incline=26.6degrees

a=2x/t^2 (rearranged kinematic equation)

a=gsin(26.6)

a=4.39 m/s^2

4.39=2x/t^2

x=.47m

.94/4.39=t^2

t=.46 s

(This solution was marked incorrect) Help would be greatly appreciated.