Just need the formulas please

[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.

[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.

[physics-dummy]

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

[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.

[physics-dummy]

Thanks for the help.