A moving 2.80 kg block collides with a horizontal spring whose spring constant is 467 N/m.

http://newcapa2.cc.huji.ac.il/res/ms...boxwallspr.gif

The block compresses the spring a maximum distance of 8.00 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.140.
1) What is the work done by the spring in bringing the block to rest?
(in J)

2) How much mechanical energy is being dissipated by the force of friction while the block is being brought to rest by the spring?
(in J)

3) What is the speed of the block when it hits the spring?
(in m/s)

(p.s: I do not have any background in physics, so I do not understand physics ! ) please help me to solve it.
Specially number 1 , because there left only one try for me, in the online essay

Thanks

1. The work done on a spring is given by:



Now, F = ke, hence we get:



where k is the spring constant and e the extension/compression of the spring.

2. Use the formula for work done.



But the frictional force is given by:

And

You have everything needed to find the work done.

3. Use the principle of conservation of energy for this one and:



where m is the mass and v the speed of the block.

What is Fe?

I need a number for the first one ! The final answer !
I know how to answer the 2 and 3 ones , sorry for pasting them..

Have you even seen an Fd graph? (force is plotted against displacement in the direction of force)

Well, for the force on a spring, you get a graph of the form:

F = ke

Where the y axis is F and the x axis is e, the extension of the spring.

Now, since k is a constant, you get a graph of the form y = mx.

And the work done by the spring is given by the area under the Fd or Fe graph.

This area is found to be also the area of a triangle, of base length e and perpendicular height F.

The work done is hence =

Quote:

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susus does not find this helpful : because I was not able to understand it

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Oh please, I'm not quite in a good mood right now and I'm very tired. READ the RULES of the site concerning homework.

I'm NOT even supposed to be helping you since you didn't post your attempt at the question and you're just copying and pasting your questions.

Is it my fault if you don't understand? I'm trying to make it as simple as possible. If you don't understand, ask for clarification. If you can't even understand the basics, then what are you doing at school? Those are problems that you should be able to solve by studying well your books and notes given to you.

I solved the 2nd question the first one.. I still can not solve it !
I tried ! But I still get the wrong answer ! There left only one try for me :( on the essay

OK so , I did try to do what u explained and I really got wrong answers
W = 0.5ke^2 = (0.5)(467)(0.08)^2 = 1.4944 J

and for the last question.. because the W I got it wrong, also I got the third question wrong !

Read my other comment ! It has one of my attempts..
I really tried to do what u did, even before u gave me the tools..

Sorry for this misunderstanding

Ah and I really appreciate what you did and what you are doing. This so amazing! U helped me to understand lots of things ! So yeah thanks !

Why should I? You'll tell me again that you didn't understand it. I gave you the correct formula, but it seems you didn't follow the class. I used specific wording and if you analysed the question and my response well, you'll see what is wrong with what you did.

Ah now I know why the first was wrong with me,]I hade to put -1.4944.. not +1.4944 :)

Guess what!! I'm done with it ! Thanks so much for helping !

Yes, that's it. The question asked for the work done BY the spring while I gave you the work done ON the spring.

From there, all the others will come in easy.