# Homework Help: Force given velocity as function of space.

1. Sep 2, 2015

### deblimp

1. The problem statement, all variables and given/known data
The speed of a particle of mass m varies with space as v(x) =ax^-n
v(x=0)=0 at t=0.
Find F(x).

2. Relevant equations
F=ma=m dv/dt

3. The attempt at a solution
I am not really sure where to start from. Would x(t) or f(t) be relevant?

2. Sep 2, 2015

### axmls

You have Newton's law defining the relationship between the force and the acceleration. You also have the velocity as a function of time. Now you need the acceleration. And you can plug that in for the force.

3. Sep 2, 2015

### deblimp

No we do not have velocity as a function of time, we have it as a function of space. Therefore we can't just differentiate and get the accel.

4. Sep 2, 2015

### insightful

Usually, these problems make use of the chain rule of differentiation.

5. Sep 2, 2015

### insightful

Is "a" acceleration or just a constant in the equation?

6. Sep 2, 2015