Ok this is just me breaking it down for myself. Please add on anything I left missing:
Force = mass * acceleration
Kinetic Friction = Coefficient of Kinetic Friction * Normal Force
Coefficient of Kinetic Friction = .25
I'm gonna read up on my sine/cosine etc and try to do this on paper.
More breaking it down:
For the 7kg block, there are four different forces on it:
Normal Force pushing up and left,
Tension1 Pulling up and right,
Weight*sin37+Kinetic Friction pulling down and left, and
Weight*cos37 pulling down and right.
*Now I assume you use 9.8 m/s/s for the acceleration of gravity? If not, then substitute whatever your class uses instead of 9.8 m/s/s.*
Weight (mg) = 68.6 Newtons
sin37 = .601815023
>>>68.6 * .601815023 = 41.28451059
>>>Force pulling left and down = 41.28451059 Newtons
cos37 = .79863551
>>>68.6 * .79863551 = 54.78639599
>>>Force pulling right and down = 54.78639599 Newtons
Due to the equal and opposite reactions, Normal force is also = 54.78639599 Newtons.
So, for the 7kg block, we have the following equation for the total force (assuming that the Normal force and the force pulling down and right cancel each other out): F = 41.28451059 - Tension1
For the 12 kg block, there are only two forces:
Tension2 Pulling up,
and weight (mg) pulling down.
mg = 117.6 Newtons
So this gives us the following equation: F = Tension2 - 117.6
Now this is where I get fuzzy...We have to find both Tension1 and Tension2. So is the tension equal to the pulling force from each block? PLEASE correct me if I'm wrong. But if so, then Tension1 = 117.6 Newtons, and Tension2 = 41.28451059.
So for the 7kg block, we have:
F = 41.28451059 - 117.6
>>> F = -76.31548941
>>> F = ma
>>> a = -76.31548941 / 7
>>> a = -10.90221277
For the 12kg block, we have:
F = 41.28451059 - 117.6
>>> F = -76.31548941
>>> F = ma
>>> a = -76.31548941 / 12
>>> a = -6.359624118
Alright...so what did I do wrong?
