Momentum - related question

Watch this thread
Thanquinho
Badges: 11
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#1
Report Thread starter 1 year ago
#1
I have been trying to solve this problem for quite a while now, I even asked one of my teachers and they found it hard and could not solve it.
So,

A stationary unstable nucleus of mass M emits an alpha particle of mass m with kinetic energy E .

What is the speed of recoil of the daughter nucleus ?

The answer is
A ) √2mE / (M-m)

I've attached a photo of the question so you also see the diagram, maybe it helps.
( https://imgur.com/8UbT5Jg )
But I do not know how to get to it. Can anyone explain it step by step please? Thank you !
0
reply
RoseVet
Badges: 15
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#2
Report 1 year ago
#2
Attachment 971332

I got this far, but I don’t know how they get the m on the top of the fraction, maybe you could work it out from here?
1
reply
ghostwalker
Badges: 17
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#3
Report 1 year ago
#3
(Original post by Thanquinho)
I have been trying to solve this problem for quite a while now, I even asked one of my teachers and they found it hard and could not solve it.
So,

A stationary unstable nucleus of mass M emits an alpha particle of mass m with kinetic energy E .

What is the speed of recoil of the daughter nucleus ?

The answer is
A ) √2mE / (M-m)

I've attached a photo of the question so you also see the diagram, maybe it helps.
( https://imgur.com/8UbT5Jg )
But I do not know how to get to it. Can anyone explain it step by step please? Thank you !

Alpha particle has mass m and kinetic energy E, so if it's speed is u, then we have E=\frac{1}{2}mu^2

And we can rearrange to get u=\sqrt{\frac{2E}{m}}.....(1)

Mass of daughter nucleus is M-m, and let it's speed be v.

Then by conservation of momentum.

mu=(M-m)v

Make v the subject and substitute for u from (1)
1
reply
Thanquinho
Badges: 11
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#4
Report Thread starter 1 year ago
#4
(Original post by RoseVet)
Attachment 971332

I got this far, but I don’t know how they get the m on the top of the fraction, maybe you could work it out from here?
Thanks !
0
reply
Thanquinho
Badges: 11
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#5
Report Thread starter 1 year ago
#5
(Original post by ghostwalker)
Alpha particle has mass m and kinetic energy E, so if it's speed is u, then we have E=\frac{1}{2}mu^2

And we can rearrange to get u=\sqrt{\frac{2E}{m}}.....(1)

Mass of daughter nucleus is M-m, and let it's speed be v.

Then by conservation of momentum.

mu=(M-m)v

Make v the subject and substitute for u from (1)
Thank you, I ve asked about 3 teachers and all of them got stuck on this question.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Year 12s - where are you at with making decisions about university?

I’ve chosen my course and my university (13)
32.5%
I’ve chosen my course and shortlisted some universities (13)
32.5%
I’ve chosen my course, but not any universities (2)
5%
I’ve chosen my university, but not my course (2)
5%
I’ve shortlisted some universities, but not my course (3)
7.5%
I’m starting to consider my university options (6)
15%
I haven’t started thinking about university yet (0)
0%
I’m not planning on going to university (1)
2.5%

Watched Threads

View All