- #1
kenway
- 13
- 1
Homework Statement
A 3 kg wood block is launched up an inclined wooden ramp that has an angle of 25° to the horizontal. the Block's initial speed is 12 m/s and the kinetic coefficient of friction is 0.2. What is the vertical height the block reaches above it's starting point? What speed does it have when it slides back down to its starting point?
Homework Equations
The Attempt at a Solution
What's listed first is what is given:
VO=12m/s
g=9.8m/s2
mass (m) = 3kg, which means
weight (w) = 29.4 N
μ=0.2
θ=25°
Then I found the x and y components of the weight:
wx = 29.4sin25 = 12.42 N
wy = 29.4cos25 = 26.65 N
The normal force and y component of the weight equal each other:
normal force (n) = wy
n=26.65 N
And by using the normal weight I found friction:
friction (f) = 0.2(26.65N) (μ*n)
f= 5.33 N
This is where I got stuck. I know if I find the acceleration in the x-direction of the block I can calculate the distance it traveled, which would give me the hyp. of the ramp (triangle) and I can use trig to find the y-comp. So if I find acceleration:
a = (wx-f)/m
a = (12.42 - 5.33)/3
a=2.63
This doesn't help because it should be negative. But then I read somewhere gravity is also acting as a resisting force, so then I modified my equation:
a = (12.42-5.33-9.8)/3
a = -0.90
But this seems low. I've tried altering that equation other times but I feel every time it is wrong. Could I get some guidance?