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winthos
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Homework Statement
A 1.0 kg mass and a 4.0 kg mass are attached to a lightweight cord that passes over a frictionless pulley. The hanging masses are free to move. What is the acceleration of the larger mass? What is the tension on the cord?
Homework Equations
F(net force)=F(tension)-weight
F=ma
The Attempt at a Solution
I found the acceleration using F=ma. The system has 3 kg of mass going down (4kg-1kg), which is equal to 29.4N of force (found by multiplying 3kg by 9.8m/s^2). The whole system has a mass of 5 kg, so I substituted into F=ma.
29.4N=5.0 kg + a
The acceleration is 5.88 m/s^2
Now comes the part I am confused about. The tension of the cord should be
F(net force)=tension-weight, or rearranged to be:
F(tension)=F(net force)+weight or (Tension=ma+mg)
I can substitute in what i know:
Tension =m(5.88m/s^2)+m(9.8m/s^2)
I am at a loss of which mass to use. Do i use the mass that i found in working on acceleration (3 kg), or the mass of the whole system (5 kg)?
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