1. Jan 13, 2004

### dragun

Heres a couple of M/C questions i can't figure out maybe someone can help me out thanks.

1. The inertia of an object is most closely related to its ?
a)volume b)shape c)density d)position e)mass

2.An object in free fall reached its terminal velocity when it has : a)no foreces
b)a constant velocity
c)reached reached the acceleration due to gravity
d)a constant increase in velocitye
e)a constant decrease in velocity

Heres some S/A i can't figure out

3.explain how the location of the Olympics affects the record for the high jump?

4. You are riding your bicycle, describe a situation where you (& your bike) have a velocity northward, but an acceleration southward?

5. State under what conditions the Law of Conservation of Energy holds?

Although I am new I hope someone can help me out or answer the questions I am desperate all help is welcomed and thanks for your help dragun

Last edited: Jan 13, 2004
2. Jan 13, 2004

### Warr

1. Inertia is the tendancy to remain at a constant velocity. Lets say you are riding on top of a car, and suddenly the car hits the brakes. Now what is going to keep you going: your volume, shape, density, position or mass? I'll also let you in on a little hint. Momentum is a factor here, and momentum = mv where m is the mass and v is the velocity, so....I hope you can figure this one out from that

2. When a terminal speed is reached, it means your acceleration is at 0. So what is the velocity if the acceleration is 0 (not looking for a number, more of a qualitative accessment of what is true of your velocity). Just so you know, the definition of acceleration is the rate of change of velocity. Hope you can figure this one out from this also.

3. The further you are from the center of the earth, the less the gravity of earth affects you, so....just the difference between doing high jump very close to the center and very far away from it.

4. Like I said before, acceleration is the rate of change of velocity. So if your velocity is changing due to a southbound acceleration, what must be happening. Here is a specific example: The bike is going 5m/s north. You are accelerating 1 m/s^2 south. 1 m/s^2 south is the same as -1 m/s^2 north. Therefore what must be happening to your velocity? If this is happening, what is physically happening to the bike/rider (like what would an observer see).

5. Hmm...I think it has something to do with a closed system. If all the changes in energy occur in a closed system, the law of conservation of energy will hold. However, in an open-system, energy can be lost to unknown sources, and therefore it doesn't 'hold' as far as what one would calculate. I could be wrong thought. The answer may just be that it always holds.

Didn't want to give the answers away...Hope it helps :)

3. Jan 14, 2004

### dragun

Thank you. You helped me a lot