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This lab will answer whether or not initial speed affects the time that a projectile is in the air.  Also, it will be determined if there is a direct relationship or not between initial speed and time.

Experimental Procedure

  1. Set the values to the following:
    1. Angle – Zero degrees
    2. Initial Speed – 10m/s
    3. Mass – 2km
    4. Diameter – 0.1m
  2. Use the tape measure to aid in raising the canon to 10.5 meters.
  3. Fire test shots to check for an accurate height of 10.5m, and erase the test shots projectiles.
  4. Start trial by firing with the preset values. Record your data.
  5. Repeat step 4, increasing the initial speed in increments of 5m/s up to 30m/s.

Experimental Data

V(m/s) T(s) X(m) Y(m)
10 1.5 14.6 -10.5
15 1.5 22.0 -10.5
20 1.5 29.3 -10.5
25 1.5 36.6 -10.5
30 1.5 43.9 -10.5

Results:  As the speed increased, the time stayed the exact same.


According to the graph and results in the table, we see that the height of the projectile is consistently 10.5 meters.  This coincides with the consistent measure of time of 1.5 seconds.  Therefore, the height, a vertical component of the projectile, is directly related to the time, and the initial speed is not related at all.  **No matter how much I increased the speed, the time remained constant throughout the trials.

Chapter 4 LAB Activity: Eratosthenes and the Earth’s Circumference Answers

By using the equation:

It is shown how the cancellation of the speed value presents the correct time value of 1.5s.

Since it was discussed that the time was affected by vertical information such as height, we also know that the vertical acceleration of all freefalling objects is -9.8m/s^2, the acceleration due to gravity.

Percent Error=


The lab fulfilled its purpose well because it displayed that various speeds do not affect the time it takes for a projectile to reach the ground.  The initial speed and the time have no relationship whatsoever.  Only vertical motion affects the time for a projectile.

Cite this article as: William Anderson (Schoolworkhelper Editorial Team), "Phet Projectile Motion Lab: Lab Answers," in SchoolWorkHelper, 2019,
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