# F=ma help

1. Dec 2, 2009

### balllla

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

what force is required to give a projectile weighing -475 N an acceleration of 3.00x10^3m/s^2

2. Relevant equations

f=ma

3. The attempt at a solution

f=ma
-175 N=m (-9.81m/s^2)
m=48.4 Kg

f=ma
f=(48.4kg)(3.00x10^3m/s^2)
f=145000 N

hi thanks so much for your help, I'm just wondering if I have completed this correct. I'm am just confused because it says that the projectile weighs -475 N so I have to change that into it's mass then into it's force.

thank you. have a good night.

2. Dec 2, 2009

### Cryxic

Seems like it's right.

3. Dec 2, 2009

### GRB 080319B

This is correct if the applied force F is horizontal. If the applied force F is vertical (upward, against weight), then

$$\sum$$F = F - mg = ma
F = m(a + g)