# Projectile motion but with resistive force

1. Sep 4, 2005

### tubworld

I have this question:

A 10kg projectile is launched with an initial speed of 100m/s at an elevation of 35 degrees. The resistive force is R = -bv , where b =10kg/s.

Determine the horizontal and vertical component coordinates of the projectile as functions of time.

How do I do this?? I urgently need the complete solution to this! Thanx!

2. Sep 4, 2005

### LeonhardEuler

Basically you're looking for a differential equation for the x-component of the velocity. This is not difficult to find because you can work with this component without thinking about the y-component. You know that $\vec{R}=-b\vec{v}$, so then $R_x=-bv_x$. You also know that $\vec{F}=\vec{R}=m\vec{a}=m\vec{\dot{v}}$, so $R_x=m\dot{v_x}$. Substitute for R. Do you recognize the solution of the differential equation you get?