# Find force from a function of displacement?

1. Sep 18, 2005

### beanryu

An object with mass m moves along the x-axis. Its position as a function of time is given by x(t)=At-Bt^3, where A and B are constants. Calculate the net force on the object as a function of time.

I have no idea as to how to begin.
Thanks for anyone's help.
I dont know !&@#%^@%!$^$(! about doing this kind of calculus problem.

2. Sep 18, 2005

### Dorothy Weglend

You want the force, so that tells you that you need to find F=ma. You know the mass, m. So you need to find a, the acceleration function for this motion.

Velocity is the rate of change of position, and acceleration is the rate of change of velocity. There are plenty of examples of this in physics, some of which are sure to be in your physics text, so you might take a look there and see how they did this.

Dot