# Find momentum

(Mentor's Note: Thread moved from general physics after being replied to, hence the lack of a template)

Find the momentum of a 50g bullet whose kinetic energy is 250J.
I know the formula to find momentum is P= mv. Please give me hints

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Bystander
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Can you find "v" from what you've been given?

Can you find "v" from what you've been given?
No, the question only gave me 50 g bullet and 250J

Bystander
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You have been given a definition/formula for kinetic energy?

Th
You have been given a definition/formula for kinetic energy?
The formula the teacher gave are p=mv and FT= delta P

Bystander
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p=mv
This is the definition of momentum, and you've indicated you understand it.
FT= delta P
"Force x time (which is impulse) equals change in momentum." The bullet before it is fired has zero velocity and zero momentum. The change in momentum then is just "mv" from the first definition. So, all you need to find now is force and time.

Are you absolutely certain you haven't been given any other definitions or formulas for kinetic energy, force, mass, work?

This is the definition of momentum, and you've indicated you understand it.

"Force x time (which is impulse) equals change in momentum." The bullet before it is fired has zero velocity and zero momentum. The change in momentum then is just "mv" from the first definition. So, all you need to find now is force and time.

Are you absolutely certain you haven't been given any other definitions or formulas for kinetic energy, force, mass, work?
No

Bystander
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Kinetic energy is defined as Ek = mv2/2 . I cannot believe that you haven't seen this in class or in the teaching materials or textbooks before being asked the original question.

ehild
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No
The problem gives mass and kinetic energy.

Find the momentum of a 50g bullet whose kinetic energy is 250J.
You should know what kinetic energy is. Look after in your lecture notes. Or you can browse the Net. See, for example: http://www.physicsclassroom.com/class/energy/u5l1c.cfm

(Attached image removed by moderator, provided the answer to the OPs homework question.)

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Örsan Yüksek

ehild
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Correct!