# Momentum of an object and kinetic energy

## Homework Statement

the momentum of an object (originally with a non zero momentum) is doubled by doubling the speed. What happens to the kinetic energy? Justify your answer you should get a numerical answer.

## The Attempt at a Solution

well i know that momentum is the product of mass and velocity and velocity has to do with speed but im not getting anywhere with this... i dont understand where a numerical value will come from someone please help me asap ranger
Gold Member
So you know that momentum increases proportionally with velocity. But do yo know the expression to find kinetic energy?

is it 1/2mv^2 ?

ranger
Gold Member
Yup. So can you take it from here?

cepheid
Staff Emeritus
Gold Member
The question you're supposed to answer is, "what happens to the kinetic energy?" When they say they want a numerical answer, they mean that they want you to answer in a quantitative way:

"The kinetic energy increases by a factor of ____," where ____ is your numerical answer,

and NOT in a purely qualitative way:

"The kinetic energy gets bigger too."

i still dont understand what numbers im using there is no numbers given....? kinetic energy is increasing? im sorry i feel stupid this is my first physics course though and my professor does not explian things well at all...

ranger
Gold Member
i still dont understand what numbers im using there is no numbers given....? kinetic energy is increasing? im sorry i feel stupid this is my first physics course though and my professor does not explian things well at all...

the momentum of an object (originally with a non zero momentum) is doubled by doubling the speed. What happens to the kinetic energy? Justify your answer you should get a numerical answer.

The way you could do this is by taking an object with a particular mass, then have it move a some velocity. Once you have the momentum, then find KE. Then they want you to double the momentum. So its like doubling the velocity. Then take the new velocity and find KE. Then you can answer the question, what happens to KE. Makes sense?

cepheid
Staff Emeritus
Gold Member
i still dont understand what numbers im using there is no numbers given....? kinetic energy is increasing?