How Do You Solve a Physics Problem Involving Multiple Blocks and Tensions?

[raychelle93]

Homework Statement

"Blocks A, B, and C are placed as in the figure and connected by ropes of neligible mass. Both A and B weigh 25.0 N each, and the coefficient of kinetic friction between each block and the surface is 0.35. Block C descends with constant velocity. a) Draw separate free body diagrams shwoing the forces acting on A and B. b)Find the tension in the rope connecting blocks A and B. c) What is the weight of block C? d) If the rope connecting A and B were cut, what would be the acceleration of C?"

Homework Equations

The Attempt at a Solution

I've gotten as far as trying to find "A" :b)
Let ' T1 ' & ' T2 ' be the tensions in the rope connecting blocks AB and BC respct.

Apply ; Newton's 2nd Law
Writing the equation of motion for mB
T1 - mBg Sin 36.9 0 - mk mBg Cos 36.9 0 - T2 = mB a -----------(i)
Writing the equation of motion for mA

T2 - mk mA g = mA a ----------------------------(ii)
Writing the equation of motion for mC

mC g - T1 = mC a ----------------------------(ii)

Add equ(i); equ (ii) & equ(iii) ; we have
to calculate the value of a & put it in equation (i) & (ii) respt, to get the value of T1 & T 2
>>Can't find a though :( Help!

 

[rl.bhat]

Hi raychelle93, welcome to PF.
Your second equation for mass A is wrong. Check it.