# Physics homework help

1. Oct 5, 2005

### dmasports

I've been having some problems with these problems, I'd appreciate any help.

1. There are 2 people standing on a roof 80 m high, person #1 throws a ball straight up in the air with an initial velocity of 20 m/s, person #2 has a replica of the ball and drops it off the roof at the same initial velocity.

How much sooner does #2 hit the ground than #1?

What is the difference in their final velocities?

What is the displacement between #1 and #2

2. There is a race between a rabit and tourtise, the rabit rests for 10 min before starting and is 50 times faster than the tourtise. The tourtis's speed is 5 cm/s, and it ends up loosing the race by 100 cm.

How longs the race?

How long does the race last?

Thanks for the Help!

2. Oct 5, 2005

### Integral

Staff Emeritus
For the first one, what is the speed of ball #1 when it returns to the roof level on the way down?

How would you find the time it takes to reach its peak of motion and return to the roof level?

What do you know of the equations of motion of a free falling object?

3. Oct 5, 2005

### dmasports

more

all that was given to us was that accleration is 9.81 m/s, besides that nothing else is known