Table of Mechanics Demonstration

List of Mechanics Equipment & Supplies

Lecture Demonstrations

Projectile Range, 1D60.40

Topic and Concept:




Shoot a projectile out of the Pasco laucnher at 45° then calculate the range for 30° or 60°, and place the target accordingly.



ID Number

Pasco Launcher

ME, Bay A5, Shelf #1

Pasco Projectiles

ME, Bay A5, Shelf #1

Target or Tape

Provide Own (2 small Trash cans)

Important Setup Notes:

Setup and Procedure:

  1. Attach the Pasco launcher to the tabletop using a C-clamps.
  2. Have a spotter ready to spot the impact point of the projectiles.
  3. The launcher has 3 spring settings, so make sure you use the same one for all launches.
  4. After loosening the proper adjustment screw, adjust the launch angle to 45° using the weighed string/protractor that is on the face of the launcher.
  5. Use the black loading rod, push one of the Pasco projectiles down the barrel to the desired spring setting ( a click will be heard for each setting reached - third click setting is the most energetic).
  6. Shoot the projectile by pulling on the yellow string attached to the launcher.
  7. Have the spotter mark the point of impact.
  8. Measure the horizontal displacement, by counting the floor tiles or using a ruler.
  9. Compare the measured range to the predicted to obtain the correction factor.
  10. Adjust the angle now to 30° and then to 60° (chosen to be give different enough results without changing the horizontal and vertical air resistance components too much) .
  11. Have one or more spotters spot the projectiles point of impact.

Cautions, Warnings, or Safety Concerns:


The equation of projectile motion for constant acceleration can be derived by starting with the acceleration and integrating twice with respect to time to find the position. The most convenient convention is to choose a coordinate system where the horizontal motion is purely in the x-direction, and the vertical motion is purely in the y-direction. The origin is then placed at the muzzle projection onto the ground.

r(t) = x(t)+y(t)

|x(t)| = v0x * t, where v0x is the x-component of the muzzle velocity.

|y(t)| = -(g/2)* t2 + v0y * t + y0 , where g is the acceleration due to gravity, v0y is the y-component of the muzzle velocity, and y0 is the height of the muzzle off the ground.

The amount of muzzle velocity in each component is purely dependent upon the angle of trajectory (i.e. the angle of the barrel relative to the ground or table). The angle is usually called θ. v0x = cos(θ)*v0 and v0y = sin(θ)*v0 where v0 is the total muzzle velocity.

In this demo, we are concerned only with the range which is our total displacement in the x-direction after the projectile comes back to the Muzzle height ( y = 0 ). If the projectile goes to the floor, then you need to know that height too, then (y = -h). To find the range, we first find the time at which y = 0 for t > 0. This occurs at t = (v0y + Sqrt(v0y2 + 2*g*y0))/ g

After plugging in this time into the x-position equation we find the range R = (v0*cos(θ)/g) * (v0*sin(θ)+Sqrt(v02*cos2(θ)+2*g*y0)) which if maximized gives a theta of 45°.

This is of course neglecting air resistance which is speed-dependent. This is why a shot is taken first then a prediction is made. Since the muzzle velocity is roughly constant (at least for the same spring setting and ignoring random error), comparison to the "air-resistanceless" equation will give an empirical correction factor. This should allow for a fairly close trajectory prediction. It will be a little off since the air resistance does have a θ-dependance.

To get the muzzle velocity, we can pull out the Pasco Interface computer and two photogates to the muzzle of the Pasco launcher. This will add a good 5 to 8 minuets to the setup time.












fw: Projectile_Range (last edited 2013-07-12 18:18:20 by localhost)