# Just need the formulas please

1. Oct 23, 2007

### physics-dummy

1. The problem statement, all variables and given/known data:

#1. You are walking on a perfectly round asteroidwith a diameter of 40km and a mass of 10 to the 16th kg. your mass is 60kg. how much will you weigh, in Newtons?

#2 a 100 kg porshe is moving at a steady speed around a cicular track waith a 1000 m radius. The porshe's centripedal acceleration is 5 m/s squared. What is teh magnitude of its velocity?

2. Relevant equations

3. The attempt at a solution

I tried a=v squared/r but it doesn't include the mass so i didn't think it's right and i've looked through all my notes and can't find a formula for the second one. For the first one i'm lost cause f=ma dont work. any help i would be grateful for, thanks.

2. Oct 23, 2007

### Dick

You are on the right track for the second one, and you don't need the mass. On the first one look up Newton's law of gravitation.

3. Oct 23, 2007

### physics-dummy

thank you very much. after i get 71 for the second answer how do i change it into km/hr

4. Oct 23, 2007

### Dick

Put units on things, ok? If you got 71m/sec and you really want to convert to km/hr, then 1m=km/1000 and 1sec=hr/3600. Now what? Units are your friends, they help you from being confused.

5. Oct 23, 2007

### physics-dummy

Thanks for the help.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook