ATTN: Physics 12 help. *convulsion*

[brokenjoker]

Ok, so I'm preparing for a physics exam which is tomorrow, and I'm currently studying Newton's law, etc, and the equation and whatnot. So, I come across this question:

A car is moving at a constant velocity of 20 km/h (5.56 m/s). How much net force is required to raise its velocity to 50 km/h (13.89 m/s) in 30 seconds? Suppose the car has a mass of 150 kg.

And this one:

If the net force of 7 N was continuously applied on 400 g object at rest, how long will it take to raise its velocity to 80 m/s?

It's asking that I find seconds and whatnot, but the equations that I have to work with don't have a time unit in them. *eye twitch*

Can someone help me? Quickly? Perferably by the end of the night.

The equations are here:

F = ma

W = mg

FN = - mg

Ff = uFn

The u thing isn't actually a u, but something weird looking. Anyways. Please help? ^__^

[Jehanne]

Originally Posted by brokenjoker

Ff = uFn

The u thing isn't actually a u, but something weird looking. Anyways. Please help? ^__^

I hope you read the applicable sections in your physics book, because it looks like the time to get answers has already past.



Anyway, that Greek symbol is mu; and the equation looks like the one for frictional force based on normal force, with mu as a coefficient of friction.

Good luck!