Factors that affect the trajectory of a projected mass.

  1. This is my physics coursework task and although I have had only minor difficulties in actually doing the work, I thought I would post some of the things that I found to verify.

    Basically, I began with saying that the initial speed (u), initial height (h), gravitational constant (g) and the angle of projection (the) all played a role in determining the horizontal displacement (d) of the projected mass.

    I varied the initial speed (u) by constructing a ramp and changing the vertical height of the mass 'up' the ramp (H). Keeping h, g constant and [tex]\theta[/tex] = 0, enabled me to find the initial speed as [tex] v = \sqrt{2gH}[/tex] (using conservation of energy).

    I then found the time it would take for the mass to hit the floor, [tex]t = \sqrt{(2h)/g}[/tex] and combining this with the value for v enabled me to find out the horizontal displacement (d) in terms of H and h. [tex]d = 2\sqrt{Hh}[/tex]

    That was the easy part. Deciding what factors made these theoretical results different from the experimental ones was a little harder.

    Obviously air resistance will be a factor, as will the co-efficient of friction on the ramp. Those were the only two factors I could see that would make a difference.

    I have a bit of a block when it comes to air resistance. I know I am wrong in thinking that air resistance is constant magnitude but varies in direction, however I am thinking it and it is annoying me.

    Now I am forgetting the entire point of the task.. damn you PF!

    (It should come to me soon, but any views so far?)
     
  2. jcsd
  3. andrevdh

    andrevdh 1,604
    Homework Helper

    If the mass was rolling down the ramp some of the potential energy would be converted to rotational kinetic energy.
     
  4. BobG

    BobG 2,346
    Science Advisor
    Homework Helper

    The magnitude of air resistance isn't constant. It increases when the velocity increases and decreases when the velocity decreases. Unless you have a wind, the air resistance always opposes the direction of motion - i.e. relative to the object's motion, the direction of air resistance is always constant.
     
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