# Equations of motion

1. Nov 9, 2006

### Logarythmic

The problem is to determine the equation of motion for a point particle on which both the gravitational force and a friction force of magnitude
$$|\vec{F}_fr| = k|\vec{v}|$$
act and to show that when the particle starts at rest, its velocity cannot exceed mg/k.
I have attached my calculations but something is wrong. The velocity cannot increase when the incline is almost flat..?

Last edited: Nov 9, 2006
2. Nov 9, 2006

### quasar987

Incline? You can't be on an incline since additionally, there is a normal force. The problem makes no mention of such thing.

Just solve the equation of motion for F=Fgrav-kv. Plug in the initial value v0=0 and show that v(t) is a monotonous function that converge assymptotically towards mg/k as t-->+infty.

3. Nov 9, 2006

### Logarythmic

Of course. Thanks :)