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Homework Statement
Two boxes are attached to opposite ends of a rope passing over a frictionless pulley as shown below. The mass of Box A is 15kg and the mass of box B is 12kg. The system is originally at rest with the bottom of box A at a height of o.85m above the floor. When the system is released, the boxes will move. Use conservation of energy to determine the speed with which Box A will contact the floor.
Homework Equations
Eg=mgΔh
Ek= 1/2 mv^2/2
ƩFy=may
The Attempt at a Solution
I started off by drawing free body diagrams of each mass, one at rest, and one in motion.
For mass A:
at rest,
ƩFy=0
Ft+Eg=0
Ft= Eg
= mgΔh
=(15kg)(9.8m/s^2)(0.85m)
Ft=125N
in motion,
ƩFy= may
Fg(A)-Ft= m(A)ay
For mass B:
at rest,
ƩFy=0
Fn-mg=0
Fn=mg
=(12kg)(9.8m/s^2)
Fn=117.6N
in motion,
ƩFy=may
Ft-Fg(B)= m(B)ay
I'm not sure if my original statement of Ft=Eg is accurate... and from this point on I don't know where to go.