- #1
guss
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Homework Statement
A 5.00-kg block (M) on a 30° incline is connected by a light string over a frictionless pulley to an unknown mass, m. The coefficient of kinetic friction between the block and the incline is 0.100. When the system is released from rest, mass m accelerates upward at 2.00 m/s^2. Determine (a) the string tension and (b) the value of m.
Homework Equations
FF = μ*Normal
a = FN/m
The Attempt at a Solution
I am going to attempt part b of this problem first because that makes the most sense to me:
To get the normal force of the block against the ramp, I did cos(30)*9.8*5 which is 42.44 N.
To get the force of the block going down the ramp neglecting friction, I did sin(30)*9.8*5, which is 24.5 N.
Then, I figured out the friction by multiplying 42.44 by .1 which is 4.244. I can then subtract 4.244 from 24.5 to get 20.256.
Now, I know that this is the force pulling up on the unknown weight that is accelerating it.
So, I know that m=FN/a, and in this case FN is 20.256, so I simply do 20.256/2 to get 10.128 kg, but this is not correct. I thought that might be the weight, so I divided that answer by 9.8 and it still wasn't correct.
Now for part a, I'm not sure if these equations I'm using are correct, and the answer is obviously not right because my answer to part b was not correct. But I'll give the equation I used so you guys can see what I did and help me incase I'm wrong:
m1*(T-W2)=m2*(W1-T)
I don't think that's the right equation for tension in this case, but I could be correct I suppose.
Thanks.