Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Projectile motion but with resistive force

  1. Sep 4, 2005 #1
    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. jcsd
  3. Sep 4, 2005 #2


    User Avatar
    Gold Member

    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 [itex]\vec{R}=-b\vec{v}[/itex], so then [itex]R_x=-bv_x[/itex]. You also know that [itex]\vec{F}=\vec{R}=m\vec{a}=m\vec{\dot{v}}[/itex], so [itex]R_x=m\dot{v_x}[/itex]. Substitute for R. Do you recognize the solution of the differential equation you get?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook