# Speed of a unit vector

## Homework Statement

Givens:
An object with a mass of 2kg has a momentum of p=<-1,-2,3>. The first two questions asked for the magnitude of the momentum and the corresponding unit vector, which i found to be 3.74 and <-0.267,-0.535,0.802> respectively. The next question asks for the speed of the object, which is where i am having trouble. Ive looked everywhere for how to determine the speed of an object from its unit vector and cannot seem to find an answer. I believe im either overlooking something simple or am simply missing a vital piece of information.

Orodruin
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What makes you think that you need to use the unit vector?

As i was typing out "but its the only thing i was given" i realized i totally forgot about the first vector set. So the correct thing to do would be to multiply the <-1,-2,3> by 2, and then take the magnitude of that? Sorry for the original post im under a lot of stress as its a sort of pop quiz that we have limited time to finish.

Orodruin
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So the correct thing to do would be to multiply the <-1,-2,3> by 2, and then take the magnitude of that?
What is the relation between velocity and momentum?

Also, always (always!) write out the units. It will help you avoid easily spotted mistakes such as this one.

• berkeman