Homework Help: Weight and Free Fall

1. Sep 26, 2006

youxcrushxme

On a planet far, far away, an astronaut picks up a rock. The rock has a mass of 5.80 kg, and on this particular planet its weight is 40.0 N. If the astronaut exerts an upward force of 43.3 N on the rock, what is its acceleration?

I thought you just did a=1/m*Fnet. The mass is 5.8, and I thought Fnet would be 43.3n+40N but my answer is not coming out right. If anyone could help me out I'd really appreciate it!

2. Sep 26, 2006

neutrino

What about the direction of the forces? Fnet is a vector sum.

3. Sep 26, 2006

youxcrushxme

I wasn't sure about that, I thought maybe -40N because that's it's weight and then the +43.3N because it's being thrown upward but it keeps saying my answer is wrong.

4. Sep 26, 2006

neutrino

You're right. It should be 3.3/5.8 ms^-2 (assuming the data is right). May be you didn't provide the answer to the required number of decimal places.

5. Sep 26, 2006

youxcrushxme

I got it, I think I may have forgotten to make the 40N negative or something...thanks so much!