miscellaneous questions

Ok, I've looked over all the problem sets up to six, and I have a few questions...

What are the exact units of a unit? km/s^2???

If you mean kg m/s^2, this is the unit of mass multiplied by the unit of acceleration, which gives you the unit of force. So the unit kg m/s^2 is the same as a Newton.

Is it always that when you are finding 'ds with known velocity and 'dt that we have to multiply avg vel * 'dt instead of just multiplying 'dt *vel?

vAve = `ds / `dt, by the definition of average velocity.

So `ds = vAve * `dt.

`dt * vel makes sense only if velocity is constant, in which case it is equal to the average velocity; otherwise you have to specify just which velocity you are talking about.

What are the units of impluse and momentum? Are they the same? is it kgm/s?

Right to both.

Impulse is F `dt, which has units of kg m/s^2 * s or kg m/s. Momentum is m v, which has unit kg * m/s or just kg m/s.

Impluse and momentum are always equal and opposite, right? So if we know that impluse is 2, momentum would be negative 2?

No. Impulse is equal to change in momentum, not to momentum, and not opposite to momentum.

If two otherwise isolated objects act on one another they exert equal and opposite impulses, so they have equal and opposite changes in momentum.

What is the deal when finding the angle. I know you use the formula tan-1(y/x) And when what is less than zero do you add 180degrees?

when x is less than 0 you add 180 deg

I think thats everything

let me know if there's more.