Help with MCQ on momentum and energy conservation

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fluffypoopies
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I dont get why the answer is A (I keep getting D) could someone explain please?

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I calculated the initial KE of the pelet to be 100J and then the final KE of them both to be 5J (using the PCLM and the KE formula), leaving 95J of GPE which gives a height of approx 100m.
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mqb2766
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Momentum would give them both moving with 10ms^-1 post impact, which would give about 5m vertical displacement.
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Driving_Mad
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(Original post by fluffypoopies)
I dont get why the answer is A (I keep getting D) could someone explain please?

Name:  Screenshot 2022-05-21 at 20-10-55 Question paper (A-level) Paper 1 - November 2020 - AQA-74081-Q.png
Views: 8
Size:  74.6 KB
I calculated the initial KE of the pelet to be 100J and then the final KE of them both to be 5J (using the PCLM and the KE formula), leaving 95J of GPE which gives a height of approx 100m.
KE after of pellet and block = 5J. Set this equal to mgh and solved.

(Mechanics is more pain than not being able to watch a functioning DAZN stream )
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fluffypoopies
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(Original post by Driving_Mad)
KE after of pellet and block = 5J. Set this equal to mgh and solved.

(Mechanics is more pain than not being able to watch a functioning DAZN stream )
Ohhh, I get that now. But you see how originally there were 100J of energy, does the remaining 95J get dissipated? I was assuming the 95J got converted to GPE whoops
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mqb2766
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(Original post by fluffypoopies)
Ohhh, I get that now. But you see how originally there were 100J of energy, does the remaining 95J get dissipated? I was assuming the 95J got converted to GPE whoops
Why is energy necessary? Momentum gives the post impact velocity of 10, then suvat gives
s = 10^2/(2g)
Admittedly, the suvat formula is basically KE and GPE. But yes, its not elastic as both bodies move with the same velocity afterwards. Its as inelastic as you can get.
Last edited by mqb2766; 4 weeks ago
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