Can you help me with college Physics questions?

[emily K]

Hi. I'm taking an online physics class and need to have the answers to these by Sun. night. I've done most of the homework but there are a few I'm stuck on. Any way you could help would be appreciated.
1) As a car moves down the highway at constant velocity, the net force on it is zero. Yet you must continue to run the engine to overcome ____.
2) If you drop a rock, its acceleration toward the ground is 10 meters/second squared. If you toss the rock down instead such that its speed is 10 m/s after tossing it, its acceleration after tossing it would be ____.
3) The NET force on a rock that weighs 2 N when you hold it at rest above your head is ___.

This is a really tough class for me so far. If you have answers to any of these, please try to explain them the best you can.
Thank you!