Projectile Motion Claims Evaluation Lab
On of the styles of questions on the AP test has you needing to evaluate claims made by “students”. There are
times where you will need to determine if their claims are true or false (and you must provide support of your
claims). Other times you may need to determine if their supporting evidence for their claims are correct or not
correct. The phrasing of the question will establish exactly what you will be evaluating.
For this lab we will be using the projectile motion simulation from PHeT. You should have the simulation in your
simulations folder on your computer.
Simulation 1: (Horizontal Launch and no air resistance, tank shell)
Student 1: The time of flight of a projectile is determined by the launch speed. The faster it goes the farther it
travels and this means it is in the air longer.
Student 2: The time of flight of a projectile is determined by the height it is launched from. The higher up the
projectile is fired from the longer it takes gravity to bring the projectile back down to the ground. How fast it
travels only contributes to the range of the projectile.
1) Using the PHeT simulation determine which student (if any) provided a correct justification for their
prediction. In the space below, please include data to support your claim.
There is an interesting issue with the vertical displacement of the projectile (height). Even if you place the
cannon on the ground and fire a horizontal shot it will give a vertical displacement of -1.2m. For this next
simulation we need to look at/consider a scenario where the vertical displacement is 0m. In order to do this we
will need to look at the axis system associated with the cannon. Please look at the screen shot below.
The horizontal axis is the “ground” for this investigation. You need to make careful observations about the
projectiles as they pass by this representation of “ground”. This will give us a same level set up that is being
investigated. You will want to raise the cannon above the grass, but we will focus issues of range to when the
projectile crosses this horizontal axis.
Scenario 2: (Constant velocity (between 10 and 15 m/s), no air resistance, tank shell)
Student 1: When launching a projectile that has no vertical displacement from launch to landing the larger the
launch angle the larger the range.
Student 2: I agree, but there has to be an angle before 90 degrees where it travels a maximum range, because
if you shoot straight up, it will come right back down.
Student 1: That makes sense. I mean if you shoot it at an angle of 0 it basically goes nowhere, and if you shoot
the projectile straight up it basically goes nowhere.
Student 2: So if you think about it, the projectile must have an increasing range as you increase the angle and
then once it gets to a maximum range then the projectile’s range must get smaller.
Student 1: So 45 degrees is in the middle of 0 and 90, so that must be the max range. Do you think that there
are two different angles for launch that will get the same range, besides 0 and 90?
2) (a) Using the PHeT simulation confirm that 45 degrees yields the maximum range for a “same level”
launch. (b) Determine a rule (if one exists) for angles that yield the same range for a “same level”
launch. (c) Using the “range” data displayed at the top see if 45 degrees is the max range for launches
other than “same level”. Provide evidence to support your claim.
Scenario 3 (you will turn on air resistance)
Student 1: If we consider air resistance, the mass will impact the trajectory of the projectile. It will not fly in
the same path as when we ignore air resistance.
Student 2: I think it is the overall size and shape, and not the mass of the projectile that is impacted by air
resistance.
Student 1: Heavier things fall faster. If I drop a pencil and a piece of paper, the pencil falls faster then the
pencil.
Student 2: There are geometry differences as well as mass differences. I still think that it’s the geometry of the
object that impacts the range of the projectile.
3) Using the PHeT simulation determine which student (if any) provided a correct justification for their
prediction. In the space below, please include data to support your claim.