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Author Topic: Springs and momentum. 1 question CIE M/j 06 5(c)  (Read 901 times)

Offline missbeautiful789

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Springs and momentum. 1 question CIE M/j 06 5(c)
« on: October 24, 2010, 09:49:34 am »
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M/j 06 5(c)
Please could someone help me with this question, im not sure which approach to use. Much appreciated  ;D
« Last Edit: October 24, 2010, 09:58:02 am by missbeautiful789 »
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Allâhumma innî a‘ûdhu bika min al-hammi wa al-hazan. Wa a‘ûdhu bika min al-‘ajzi wa al-kasal.

Wa a‘ûdhu bika min al-jubni wa al-bukhl. Wa a‘ûdhu bika min ghalabat id-dayni wa qahr ir-rijal.

{Oh Allah, I seek refuge in You from worry and grief, from helplessness and laziness, from cowardice an

Offline Deadly_king

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Re: Springs and momentum. 1 question CIE M/j 06 5(c)
« Reply #1 on: October 24, 2010, 10:25:09 am »
I take it that you found the solution to part (b)

Work done by spring = 1/2 k ( x22 -  x12)

c) You should find out the gain in strain energy of spring using the equation above. But you need to convert k in Nm-1 first. Hence k = 1600Nm-1

Gain in energy strain energy for both springs = 1/2(1600)(0.062 - 0.0452) + 1/2(1600)(0.032 - 0.0452) = 0.36 J

Strain energy gets converted into kinetic energy of trolley.
K.E = 1/2mv2 = 0.36

Taking m as 0.85kg ----> V = 0.92 ms-1

Hope it helps :)
« Last Edit: October 24, 2010, 10:29:47 am by Deadly_king »
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Offline missbeautiful789

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Re: Springs and momentum. 1 question CIE M/j 06 5(c)
« Reply #2 on: October 24, 2010, 11:43:14 am »
I used the formula from b.
my problem is:
I found that the work don to the right is 1.26J
And the work done to the left is -0.9J
so shouldn't the total work done on the mass be 1.26-(-0.9) to the right
so instead of 0.36, why isn't it 2.16J

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Allâhumma innî a‘ûdhu bika min al-hammi wa al-hazan. Wa a‘ûdhu bika min al-‘ajzi wa al-kasal.

Wa a‘ûdhu bika min al-jubni wa al-bukhl. Wa a‘ûdhu bika min ghalabat id-dayni wa qahr ir-rijal.

{Oh Allah, I seek refuge in You from worry and grief, from helplessness and laziness, from cowardice an

Offline Deadly_king

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Re: Springs and momentum. 1 question CIE M/j 06 5(c)
« Reply #3 on: October 24, 2010, 12:44:25 pm »
Quote from: missbeautiful789 on October 24, 2010, 11:43:14 am
I used the formula from b.
my problem is:
I found that the work don to the right is 1.26J
And the work done to the left is -0.9J
so shouldn't the total work done on the mass be 1.26-(-0.9) to the right
so instead of 0.36, why isn't it 2.16J



Hehe.........my dear missbeautiful789

Energy is a scalar quantity. So it cannot be negative ;)
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Offline missbeautiful789

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Re: Springs and momentum. 1 question CIE M/j 06 5(c)
« Reply #4 on: October 24, 2010, 01:29:41 pm »
Doh.. :o
thats what you get for blindly following formulas

+Rep DK
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Allâhumma innî a‘ûdhu bika min al-hammi wa al-hazan. Wa a‘ûdhu bika min al-‘ajzi wa al-kasal.

Wa a‘ûdhu bika min al-jubni wa al-bukhl. Wa a‘ûdhu bika min ghalabat id-dayni wa qahr ir-rijal.

{Oh Allah, I seek refuge in You from worry and grief, from helplessness and laziness, from cowardice an

Offline Deadly_king

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Re: Springs and momentum. 1 question CIE M/j 06 5(c)
« Reply #5 on: October 24, 2010, 02:18:17 pm »
Quote from: missbeautiful789 on October 24, 2010, 01:29:41 pm
Doh.. :o
thats what you get for blindly following formulas

+Rep DK


Hahahaha..........guess you are right :D

You should be glad you made the mistake here and not in exams ;)
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