Revision sem1 q1

If 20 Joules of work is done in compressing a spring from 0 cm to 6 cm then find the work done in compressing the same from 3 cm to 6 cm.

7 Answers

269
Astha Gupta ·

sir...is the answer 10 joules.....????

206
Sayantan Hazra ·

show all the steps plz....and this is not the correct answer... :(

337
Sayan Sinha ·

U=12ky2
Or, U ∞ y2

So, U1U2=y1y2 whole ^2

So,
20U2=6-06-3 whole ^2

=> U2=5

Ans: 5 joules.

206
Sayantan Hazra ·

Since U is dependent only on position, so U changes at every y......this directly implies that y ≠difference in positions.......

206
Sayantan Hazra ·

Hint:
From Work-energy theorem,
U = 12kx2
or, U2 - U1 = 12kx22 - 12kx12

Use this to obtain the answer :)

337
Sayan Sinha ·

Sir, please give the answer. I am utterly confused...

206
Sayantan Hazra ·

From W.E Theorem,
Work done = Change in KE
or, Work done = Change in PE (since PE + KE for any system = constant)
or, W = U2 - U1

For given case, W = 20 J; x1 = 0 cm ; x2 = 6 cm ;

Thus, we get W = U2 - U1
or, 20 = 12kx22 - 12kx12

Solve for k........

Now use the value of k by putting x1 = 3 cm ; x2 = 6 cm ;
in the same equation to find W......and you are done!! :)

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