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Find speed given mass, force, and distance

  1. Oct 28, 2012 #1
    1. An 88-g arrow is fired from a bow whose string exerts an average force of 110 N on the arrow over a distance of 78 cm. What is the speed of the arrow as it leaves the bow?



    2. I'm completely lost, sorry!
     
  2. jcsd
  3. Oct 28, 2012 #2
    You know the force and mass of the arrow, so you can calculate the acceleration:

    F=ma

    then using equations of motion for constant acceleration, meaning the force providing the acceleration doesn't change throughout the motion.

    v^2 = u^2 +2as,
    v=final velocity, u = intial velocity=0, a=(f/m), s is distance over which the object is accelerated.

    ill check your answers once you have applied yourself :).
     
  4. Oct 28, 2012 #3

    Nugatory

    User Avatar

    Staff: Mentor

    DannyR's answer is right, but it's not the only possible way of solving the problem.

    You could also use W=Fd to calculate the kinetic energy of the arrow, use the formula for kinetic energy as a function of velocity to get the speed. An easy way to check your work is to see if you get the same answer both ways.
     
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