Register to reply

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

by Paul36
Tags: earth, spring, work
Share this thread:
Paul36
#1
Apr24-10, 03:11 AM
P: 2
1. The problem statement, all variables and given/known data
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.
2. Relevant 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
3. 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.
Phys.Org News Partner Science news on Phys.org
Security CTO to detail Android Fake ID flaw at Black Hat
Huge waves measured for first time in Arctic Ocean
Mysterious molecules in space
inutard
#2
Apr24-10, 04:11 AM
P: 93
Part B mainly requires for you to calculate the difference in the kinetic energy.
Doc Al
#3
Apr24-10, 08:36 AM
Mentor
Doc Al's Avatar
P: 41,319
Quote Quote by Paul36 View Post
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?


Register to reply

Related Discussions
Work done to stretch a spring vs Work done by a spring? Classical Physics 11
Work Done on the Mass by a spring in the horizontal plane perpendicu to earth center Classical Physics 1
Work done on the Earth by the Sun Introductory Physics Homework 2
Is earth doing work on the moon? Introductory Physics Homework 3
Calculating Work Advanced Physics Homework 3