G481 Mechanics 20 May 2014 Unoffical mark scheme

Hello,
Please could you tell me are there 2 possible answers for the second last one ? Because theres 2 equations for springs energy - e=kxsqared and e=0.5xfxX. I used the latter and got 0.06 along along with some of my friends, is this right or how many marks will I get for it?
Thanks

There is only 1 answer. I used 1/2*k*x^2 because the force pulling the spring down is no longer 3N because they stated in the question that it is pulled down further so the force has changed from 3N. Since you don't know the force you just use 1/2 * K*X^2 instead.
For figure 7.1, you can use either equation and you will get the same answer (0.09J), but for the second one the answer should be (0.25J). Therefore the answer is 0.25-0.09=0.16J

Reply 101

elias_123

5

For the question with the crane, I used the wrong height :frown:

75 m how many marks do you reckon I would get? I went on to do the percentage and got 25%

Reply 102

teachercol

OP

9

Original post by aa634

There is only 1 answer. I used 1/2*k*x^2 because the force pulling the spring down is no longer 3N because they stated in the question that it is pulled down further so the force has changed from 3N. Since you don't know the force you just use 1/2 * K*X^2 instead.
For figure 7.1, you can use either equation and you will get the same answer (0.09J), but for the second one the answer should be (0.25J). Therefore the answer is 0.25-0.09=0.16J

If you work out the new force as 5.0N and use that you can get the same answer.
0.16J either way.

Reply 103

teachercol

OP

9

Original post by elias_123

For the question with the crane, I used the wrong height :frown:

75 m how many marks do you reckon I would get? I went on to do the percentage and got 25%

If everything else was correct, I'd expect 3/4.

Reply 104

aa634

Original post by teachercol

If you work out the new force as 5.0N and use that you can get the same answer.
0.16J either way.

Yes, but it is quicker to just substitute 50 and 0.1 into 1/2*k*x^2

Reply 105

elias_123

5

For the question to determine the acceleration of free fall, what If I just didn't mention that we take the average, but mentioned everything else, would I still get full marks on it?

Reply 106

sagar448

4

I am pretty sure yes because i did the same and also on another past paper the mark scheme didnt ask for sn average

Reply 107

Hbomb777

I am very worried about this exam I was predicted a B but I think I may have gotten a D or even an E depending on the grade boundaries...In coursework I got 35/40 which is a B grade if I was to get a good A in g482 what would my overall grade approximately be? I am so very disappointed especially since I realised my mistakes when I looked over them five minutes before the end however it was too late at that point to rectify them...I was never confident in this exam and I think my sheer panic and rushing without reading the questions properly have severely affected my exam :frown:

Reply 108

furryface12

21

Original post by Hbomb777

I am very worried about this exam I was predicted a B but I think I may have gotten a D or even an E depending on the grade boundaries...In coursework I got 35/40 which is a B grade if I was to get a good A in g482 what would my overall grade approximately be? I am so very disappointed especially since I realised my mistakes when I looked over them five minutes before the end however it was too late at that point to rectify them...I was never confident in this exam and I think my sheer panic and rushing without reading the questions properly have severely affected my exam :frown:

It depends on UMS what grade you'd get, but G482 accounts for 50% of AS so I wouldn't worry too much just yet, concentrate in getting the best mark you can in it! :smile:

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Reply 109

mwatters

What's the general consensus as to what raw mark would be needed for 90/90 UMS?

Reply 110

Hithere098765432

Original post by sagar448

I am pretty sure yes because i did the same and also on another past paper the mark scheme didnt ask for sn average

I said measure the height from the position where u going to release till the ground level and then i said start the stopwatch as soon as u release and stop as it touches the ground find g using the equation i mentioned and said do the same to find g for different heights...,
What would i get any idea???

Reply 111

Hithere098765432

Original post by aa634

There is only 1 answer. I used 1/2*k*x^2 because the force pulling the spring down is no longer 3N because they stated in the question that it is pulled down further so the force has changed from 3N. Since you don't know the force you just use 1/2 * K*X^2 instead.
For figure 7.1, you can use either equation and you will get the same answer (0.09J), but for the second one the answer should be (0.25J). Therefore the answer is 0.25-0.09=0.16J

What if i put my answer as 0.25 because i completely had no idea u take away the two from each other.. :/ would i get any mark?

Reply 112

sagar448

4

Original post by Hithere098765432

I said measure the height from the position where u going to release till the ground level and then i said start the stopwatch as soon as u release and stop as it touches the ground find g using the equation i mentioned and said do the same to find g for different heights...,
What would i get any idea???

I think you'll be fine 3/3