- #1
musicfairy
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In Figure 7-52, two identical springs, each with a relaxed length of 50 cm and a spring constant of 400 N/m, are connected by a short cord of length 10 cm. The upper spring is attached to the ceiling. A box that weighs 105 N hangs from the lower spring. Two additional cords, each 85 cm long, are also tied to the assembly, and they are limp.
(a) If the short cord is cut, so that the box then hangs from the springs and the two longer cords, does the box move up or down from its initial location?
(b) How far does the box move?
(c) How much total work do the two spring forces (one directly, the other via a cord) do on the box during that move?
The springs are supposed to change from series to || when the cord is cut. I have a very hard time visualizing what it would look like.
For part a it moves up.
For part b I try to solve for the length of the whole thing by adding the length of the spring and cord, then solving for how far it stretches.
F = kx
105 = 400x
x = 0.26 m
Since there's 2 spring the length stretched would be 0.52 m
So I added the distance stretched to thye length of the two springs and the short cord, and got 1.02 m.
Now I have to figure out the new length. The 2 springs are in ||, so they'll stretch half as much. What I don't know is what to do with the 2 springs. I can't visualize, so I can't solve for the change in length.
I can't do part c unless I have unless I get an answer from part b. I assume that the work done would be be the change in distance stretched? I'm not really sure.
Please help.
(a) If the short cord is cut, so that the box then hangs from the springs and the two longer cords, does the box move up or down from its initial location?
(b) How far does the box move?
(c) How much total work do the two spring forces (one directly, the other via a cord) do on the box during that move?
The springs are supposed to change from series to || when the cord is cut. I have a very hard time visualizing what it would look like.
For part a it moves up.
For part b I try to solve for the length of the whole thing by adding the length of the spring and cord, then solving for how far it stretches.
F = kx
105 = 400x
x = 0.26 m
Since there's 2 spring the length stretched would be 0.52 m
So I added the distance stretched to thye length of the two springs and the short cord, and got 1.02 m.
Now I have to figure out the new length. The 2 springs are in ||, so they'll stretch half as much. What I don't know is what to do with the 2 springs. I can't visualize, so I can't solve for the change in length.
I can't do part c unless I have unless I get an answer from part b. I assume that the work done would be be the change in distance stretched? I'm not really sure.
Please help.