How do you find the tension in this problem?

Question

Two blocks, of weight 3.6 N and 7.2 N are conected by a massless string and slide down a 30 degree incline plane. The coefficient of kinetic friction between the lighter block and the plane is .10; that between the heavier block and the plane is .20. Assuming that the lighter block leads, find the tension in the string and the acceleration of the blocks.

Answer 1

The basic formula is: F=Ma, where F is the net force acting on both blocks in N, M is the total mass of both blocks in kg, and a is the acceleration of both blocks in m/s^2.

Draw the inclined plane showing the two blocks, the components of their respective weights along the incline and normal to the incline, their respective mass, and the forces of kinetic friction acting on each block.

If you now have the diagram, the weight component of the 3.6N block along the incline=3.6sin30; the weight component of the 7.2 N block along the incline=
7.2sin30.Their direction is parallel to the incline
going down.

The opposing forces are the kinetic friction on each block. Use the formula, f=uR where f=the force of
kinetic friction along the incline, u the coefficient of kinetic friction, and R the the weight component of each block normal to the incline.

Substitute known values:

f of 3.6N block=0.10*3.6cos30
f of 7.2N block=0.20*7.2cos30

total of both f=0.10*3.6cos30+0.20*7.2cos30
Their direction is opposite the weight components.

Therefore, net total force:

F=3.6sin30+7.2Sin30
-(0.10*3.6cos30+0.20*7.2cos30)
=3.6*0.5+7.2*0.5
-0.10*3.6*0.866-0.20*7.2*0.866
=1.8+3.6-0.31-1.25
=3.84N

Substitute this value in F=Ma
3.84=[(3.6+7.2)/9.8]a
3.84=1.10a
a=3.84/1.1
=3.49m/s^2

Tension in the string:

The net force on the 3.6N block:
F'=ma=[3.6/9.8]*3.49
=1.28N
Tension in the string=F'+force of kinetic friction
=1.28+0.31
=1.59N

Answer 2

Dang, I'll need my science notes on that, but break out the highligter and highlight the things you belive that are important. The weight is 3.6N and the 7.2 N connected by massless string...and slide down a 30 degree incline plane, the KF is between the lighter block, lets see...the tension is the heaver block. I think, sorry if I'm wrong, I tried that one confused me more than my science teachers pet cockroach!

Answer 3

in the middle is my educated guess