Video: Motion in Two Dimensions 2D Projectile Motion Experiments

These activities are great addditions to a study of forces and motion. In the first experiment students push two pennies off a table: one simply falls and the other is launched horizontally. Regardless of how far or fast the one penny is launched, both hit the ground simultaneously. This simple demonstration shows that horizontal speed and vertical acceleration are independent. This surprising fact is fundamental to understanding projectile motion.

In the second experiment, students prop a table or desk so that it slants and then set up a ramp perpendicularly. When a marble is rolled down this ramp it gains horizontal speed and when it rolls onto the slanted table, it gains vertical acceleration. Combining these two motions results in the classic parabolic curve of projectile motion. Wetting the ball makes a track of its motion so students can clearly see its shape. Continually rolling the ball down the ramp demonstrates the repeatability of the experiment.

Students can independently adjust the horizontal and vertical speeds to show how each affects the resulting parabolic path and begin to understand that the shape of falling objects is due to constant horizontal speed combined with accelerating vertical speed.

This video demonstrates and supports the written instructions which can be found at the link here, however both the video and the written instructions can work independently if desired.

Motion in Two Dimensions 2D

Concepts Addressed
• All objects fall at the same rate whether or not they’re moving horizontally.
• A thrown object makes a parabolic path.
• Projectile flight can be steeper or gentler but is always parabolic.
Materials Needed
steel ball or marbles, large pieces of newsprint, cup of water, grooved ruler, coins

Answer Key
Extensive teacher notes address the many questions that come up. You shouldn’t have to do outside research on this topic unless you want to.

Time Required
This first lab takes about 20 mins, the second will take about 45 minutes but can take longer.

Student Sheets
• Scaffolded writing prompts & lab reporting

Other resources
Click here to see written directions for these two labs:
Motion in Two Dimensions 2D

Click here to see companion curricular pieces:
Activities on Motion (Newton's Laws)


Virginia VA SOL
PS.10 a, b, c

Texas TEKS
Grade 6: 8B
Grade 8: 6A, 6B, 6C

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