Speed before impact of an object falling down a slope.

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DAN393
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Homework Statement


A 4.7 kg block is placed on an incline with a 14° angle.
Ignoring friction, what is the acceleration of the block?
If the coefficient of kinetic friction is 0.25 (and has overcome static friction) what is the acceleration of the block?
If the incline is 4.6m long, what is the velocity of the block at the bottom (considering friction)?

Homework Equations


Ff=μFn
Fn=FgCosθ
Fg=4.7kg*9.81m/s^2
F=ma
Force on block due to gravity = 11.15N

The Attempt at a Solution


To find the first part, I used Fnet=ma, rearranged to find a and found the acceleration without friction to be:
FgSinθ/m = 46sin14°N/4.7kg = 2.36m/s^2

Then I calculated Ff to be 11.18N, which means there is no movement, and that is where I'm stumped because the last question would lead one to think that it moved somewhat.
 
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