# Homework Help: Physics homework need help

1. Jan 13, 2005

### stephenthe1

physics homework need help!!!

hi, I'm a student in eleventh grade. I'm actually working on a test for tomorrow, that, to be honest, I'm really not ready for. It's just regular, 1st year phyiscs.

ok, well, my first question I need help with is as follows.

When a punter kicks a football, is he doing work on the ball while his toe is in contact with it? Is he doing work on the ball after the ball loses contact with his toe? Are any forces doing work on the ball while the ball is in flight?

2. Jan 13, 2005

### dextercioby

What's your opinion??You're not expecting us to give you the answers right away,you have to figure them out yourself,maybe with a little help from us.

Daniel.

3. Jan 13, 2005

### stephenthe1

no, I need to know why so I can do understand for the test. I feel kind of dumb for such basic stuff, but. I think the punter IS doing work on the ball while it is in contact, then no work when not in contact. air resistance and gravity are the forces.

4. Jan 13, 2005

### dextercioby

Second part,perfect.However,the first part needs rethinking.Take into account the definition of work.

Daniel.

5. Jan 13, 2005

### stephenthe1

you mean, because the distance between the ball and the punter isn't changing that work is never being done.

6. Jan 13, 2005

### dextercioby

That's right.During the time the toe/foot/sports shoe and the ball are in contact,there's no "delta x" (meaning it is zero) and by the time they lose contact,there is "delta x",but the force is zero.

Daniel.

7. Jan 13, 2005

### stephenthe1

A weight is connected to a spring that is suspended vertically from the ceiling. If the weight is displaced downward from its equilibrium position and released, it will oscillate up and down. How many forms of potential energy are involved? If air resistance and friction are disregarded, will the total mechanical energy be conserved?

to be honest, I have no idea on this one. I would think the total mechanical energy would be conserved, because the spring would keep oscillating. and I don't know what different forms of potential energy are.

8. Jan 13, 2005

### dextercioby

What kind of conservative forces (the ones that come from potential fields/potential energy) are involved??Actually,which??

Daniel.