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Momentum question help A2 Physics

Hello, I have attached a photo of a question I need some help with, I have a possible answer but I need it to be checked, if you could let me know what answers you get that would be great, many thanks!

image.jpg
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Reply 2
Avatar for 7jdrabble
7jdrabble
OP
Thanks for the reply, for the first part I got 336 x10^3 (rounded) and the second part I am going through now, I will find out the correct answers tomorrow anyway but I was told these were top level questions so they will be a bit of a challenge
Reply 3
Avatar for HarryW95
HarryW95
How did you get 3.41x10^5? I seem to have calculated b) the same way as you though, although using a slightly different value for the speed of recoil.

a) momentum before = momentum after 0 = 0

p=mv
2.0x10^7 x 4 = 8.0x10^7 kgms^-1

8.0x10^7 / 238 = 3.361x10^5

b))KE of alpha particle / total KE) x 100

Using 1/2mv^2:
KE of alpha:8.0x10^14
KE of atom: 1.345x10^13
Total energy: 8.134x10^14

(8.0x10^14/8.134x10^14)x100 = 98.35%
Reply 4
Avatar for 7jdrabble
7jdrabble
OP
Yes we certainly did, thank you for checking that!
Reply 5
Avatar for 7jdrabble
7jdrabble
OP
Thanks everyone for your help!
Reply 6
Avatar for HarryW95
HarryW95
Ahh you're right, I didn't consider that the initial atom would lose mass after emitting the alpha particle. Thanks. :smile:

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