simple momentum and force problem

Question

vocaloid · Answer

an object moves in the x direction with a momentum of 8 kg * m/s. a force with Fx = -9N and Fy = 3N acts on the object for 0.15 seconds. what is the magnitude of the velocity after the 0.15 seconds have passed?

my thought is to use the momentum update principle (final momentum = initial momentum + Fnet*deltaT) but I'm not sure how to set things up

abhisar · Answer

So mass of the object is not given?

vocaloid · Answer

no

irishboy123 · Answer

you need the mass to get velocity

vocaloid · Answer

@IrishBoy123  made a typo, it wants the magnitude of the momentum after 0.15 seconds. would I still need the mass for that?

irishboy123 · Answer

nope, you're now good to go! i would do something like $$\vec p_o = <8,0>$$ $$\vec F = \frac{d \vec p}{dt} \implies \Delta \vec p = \vec F .\Delta t$$ $$\therefore \vec p = <8,0> + 0.15<-9,3>$$ $$|\vec p| = \sqrt{p_x^2 + p_y^2}$$

vocaloid · Answer

that's what I was thinking, too, I just had my numbers set up wrong

I got the answer, thanks for your help ^_^

NineTailedFox · Answer

holy crap. this was a long time ago