Calculating Tension in Ropes A & B

[jamessmith]

Homework Statement

I have a 1 kg ball hanging from rope A, and a 2 kg ball connected to the 1 kg ball by rope B. They are accelerating up at 4.0 m/s^2. I need to know the tension in rope A and rope B.

Homework Equations

Tension = Fg + ma ?

The Attempt at a Solution

Rope A: (1 kg + 2 kg) * (9.8 m/s^2) + (1 kg + 2 kg) * (4 m/s^2) = 41.4 N
Rope B: (2 kg) * (9.8 m/s^2) + (2 kg) * (4 m/s^2) = 27.6 N

Am I doing this correctly?

 

[noblegas]

I think since the ropes are accelerating in the vertical direction , the sum of all forces acting on the ropes with the attached ball will be equal to an accelerating force, not zero. Have you sketched a free body diagram of all the forces acting upon the two ropes? .

 

[Redbelly98]

The Attempt at a Solution

Rope A: (1 kg + 2 kg) * (9.8 m/s^2) + (1 kg + 2 kg) * (4 m/s^2) = 41.4 N
Rope B: (2 kg) * (9.8 m/s^2) + (2 kg) * (4 m/s^2) = 27.6 N

Am I doing this correctly?

Looks good!

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