Masses on incline plane and pulley.

[i<3physics]

Homework Statement

A suspended 2.87 kg mass is moving up, a 1.5 kg mass slides down the ramp, a suspended 8.4 kg mass on the left is moving down. There is friction between the block and the ramp. The acceleration of gravity is 9.8 m/s2 . The pulleys are massless and frictionless.

Find the acceleration of the 3 block system.
Here is a diagram

http://img8.yfrog.com/i/capturexki.jpg/

Homework Equations

F=ma
Friction=μN
F parallel: mgsinφ
F perpendicular: mgcosineφ

The Attempt at a Solution

Sumation equation I set up (mass 1= 8.4kg, mass 2=1.5kg, mass 3=2.87kg mt=total mass)

m1g-m2g(sinφ)-friction-m3g=mtg

after the numbers are plugged in:

(8.4)(9.8)-(1.5)(9.8)sin36-(0.14)(1.5)(9.8)cos36-2.87(9.8)=12.77a

acceleration would equal=3.43 m/s2

is this correct?

 

[Jshua Monkoe]

i think your attempt is exactly what the question required

 

[i<3physics]

I figured it out...

I was forgetting to add the parallel force to the driving force.

All is well now, thanks!