- #1
Phoenixtears
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Homework Statement
A 3.2 kg wood block is launched up a wooden ramp that is inclined at a 20° angle. The block's initial speed is 8 m/s. (Use µk = 0.20 for the coefficient of kinetic friction for wood on wood.)
(a) What vertical height does the block reach above its starting point?
_____m
(b) What speed does it have when it slides back down to its starting point?
_______m/s down the ramp
Homework Equations
Delta-x= V0*t + .5a(t^2)
Vf^2= V0^2 + 2ax
Vf= V0 + at
F=Ma
The Attempt at a Solution
I don't really understand one aspect of this problem, which I think is the thing that is throwing everything else off. I began by drawing a force diagram and then a horizontal vs. vertical table with initial and final veloctiy, delta-x, acceleretion, and time. We can find the vertical and horizontal inital velocity because we are given the angle and the inital velocity.
Initial Vertical- 8cos20= 2.7362
Inital Horizontal- 8sin20=7.5175
Now here's the part that's throwing me off. I know that to find a) we can say that the final velocity is 0, but wouldn't the acceleration be 9.8? I thought so, but that answer is not correct. I can't figure out what I am doing wrong. Any suggestions?
Also, for b), I don't understand why 8 is not the answer. Is it not a law that the velocities will be the same at the same location?
Thank you,
Phoenix