Calculating Work done by the Earth and the work done by the Spring

AI Thread Summary
The discussion revolves around calculating the work done on a mass hanging from a spring as it moves downward. For part (a), the work done by the Earth is calculated using the formula F times displacement, yielding approximately -0.080262 Joules, with the sign indicating the direction of the force relative to displacement. In part (b), the focus shifts to determining the work done by the spring, which requires calculating the change in kinetic energy as the mass's speed decreases from 3.80 m/s to 2.13 m/s. The sign of the work done is crucial, as it depends on the direction of the force compared to the displacement. The net work done on the mass is also a key consideration in understanding the overall energy changes in the system.
Paul36
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Homework Statement


A mass of 0.091 kg hangs from a vertical spring in the lab room. You pull down on the mass and throw it vertically downward. The speed of the mass just after leaving your hand is 3.80 m/s.

Homework Equations


(a) While the mass moves downward a distance of 0.09 m, how much work was done on the mass by the Earth? Include the appropriate sign.
Work done by Earth = ...Joules

(b) At the instant in part (a) when the mass has moved downward a distance of 0.09 m, the speed of the mass has decreased to 2.13 m/s. How much work was done on the mass by the spring? Include the appropriate sign.
Work done by spring = ...Joules

The Attempt at a Solution


To calculate Work I'm using the formula F times displacement
So for (a) I calculated:
0.09m X -9.8m/s/s X 0.091kg = -0.080262J
is that correct?
For part B I have no idea what to do?
Thanks if you can help.
 
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Part B mainly requires for you to calculate the difference in the kinetic energy.
 
Paul36 said:
To calculate Work I'm using the formula F times displacement
So for (a) I calculated:
0.09m X -9.8m/s/s X 0.091kg = -0.080262J
is that correct?
Except for the sign. What determines the sign of the work done is whether the force and displacement are in the same direction or not. If they are, the work done is positive.
For part B I have no idea what to do?
What's the net work done on the mass?
 
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