a=change in velocity/time, is this the formula i use for this question:

Question

a car takes 5 seconds to speed up from 10 m/s to 60 m/s. what is the acceleration?

yes!

so what do i do from there?

If it goes from 10 to 60, what is it's CHANGE in velocity (speed)?

is it 50

Yes...so now you know the change in velocity, and the time, so you can plug them into your formula.

i have 50/5 i divide right or wrong

Right! you divide.

so a=10

You got it!

ok thx now can u help me through the steps to this question?
what is the momentum of a 500kg object moving at 10 m/s?
is it p=mv

That is the correct formula, and you have all the information. 500 kg is the mass, m, and 10 m/s is the velocity, v.

so its p=500x10

correct.

so p=5000

correct

this is were i get stuck:
how much force is neede to stop in 20 seconds?

Please post this as a new question, and complete the question...how much force is needed to stop what in 20 seconds?