Energy Conversions calculations question (1 Viewer)

leehuan

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Have no idea how to do this one. Apparently the answer is B.
Screen Shot 2016-08-04 at 9.34.05 pm.png
 

InteGrand

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The above by Fizzy_Cyst is what I was doing too, but it is an answer well smaller than the one leehuan said is apparently the right answer.

It would be:

mgh – 1/2 mv^2 = m(g – 1/2 v^2) (as h = 1)

= 0.1 * (g – 1/2 v^2).

Since v = 3.8, v^2 = (4 – 0.2)^2 = 16 – 1.6 + 0.04 = 14.44 (didn't have calculator on hand lol).

So we'd get the answer to be: 0.1 (9.8 – 7.22) =~ 0.1*(2.6) = 0.26. So the answer is much smaller than B), and should be D) I think... . leehuan, how do you know the answer is B)? Was there any working too, or just the answer given?
 

leehuan

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At this point almost everyone I've consulted has said the answer is B. And by the exact same reasoning which I agree with.

Yeah, sometimes I question the reliability of the people who ask me (or rather 'us') questions.
 
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Fizzy_Cyst

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How have they explained the answer as being B?

It's an impossible answer!

Change in Ep is only mgh = 0.1x9.8x1 = 0.98J. Can't get 3.7J transformed into other types of energy if there is only 0.98J to play around with in the beginning, it violates LOCOE!

Answer is definitely D.
 
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leehuan

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I'm trying to get the source of the Q.
 

Fizzy_Cyst

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I just had a look through my papers as I thought i recognised the font.

It's from the 2013 Exam Choice Paper, the answer is D in the marking criteria.

/high5sintegrand lol
 

Nailgun

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I just had a look through my papers as I thought i recognised the font.

It's from the 2013 Exam Choice Paper, the answer is D in the marking criteria.

/high5sintegrand lol
and now I have a whole new set of past papers that I need to do lol

I hope the other questions are of similar trickiness lol
 

leehuan

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Don't blame me if people messed up reading the answers or something

But I'll let the other people that did the question know
 

Fizzy_Cyst

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and now I have a whole new set of past papers that I need to do lol

I hope the other questions are of similar trickiness lol
Nah, Exam Choice are usually pretty straight forward. They have the odd good question here and there, but most are pretty standard.
 

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