# Thread: How do I solve this

1. ## How do I solve this

A 3-kg particle has a velocity of (3i - 4j) m/s. Find the magnitude of its momentum.

2. Originally Posted by jaycas21
A 3-kg particle has a velocity of (3i - 4j) m/s. Find the magnitude of its momentum.
Momentum:

$
p=mv
$

so:

$
|p| = m|v| = m\sqrt{3^2+4^2}=5m \mbox{ kg.m/s}
$

RonL

3. ## No I got it also

Yes I got that too but the answer are as follows:

9 kg.m/s

-12 kg.m/s

15 kg.m/s

3 kg.m/s

4. Originally Posted by jaycas21
Yes I got that too but the answer are as follows:

9 kg.m/s

-12 kg.m/s

15 kg.m/s

3 kg.m/s
If you look carefully at CaptainBlack's work you will see that he simply forgot to multiply by m. His answer is the magnitude of the velocity, so the answer is 3*5 kg m/s = 15 kg m/s.

-Dan