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# A Level Physics Unit 2 Question watch

1. I am confused at why for this question (http://imgur.com/a/1kQxH) to calculate the work done on the spring to squeeze it, the equation is
W= f*d*0.5 and not W=f*d.
Thanks!
2. I think that equation is in the formula booklet? E=1/2Fx where E is work done, as it is the energy transferred to the spring.

An explanation as to why there is a half there....

Imagine drawing a force-extension graph for the spring. What will it look like? The hint is that it follows Hooke's Law.

Spoiler:
Show

http://www.one-school.net/Malaysia/U...asticgraph.png

Okay, so it is going to look like the image above (sorry, the image wouldn't show up, but the link will take you to one!!)

The area under the graph is the work done. (This is because when you integrate F with respect to x, you get Area = Fx = Work done.)

But you can't use W=Fd because:

What's the formula for the area of this triangle? One of the sides will be F and the other will be x. This equation is what you use for the work done by a spring, when the spring follows Hooke's Law.

3. Thanks for the help

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Updated: January 26, 2017
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