Only the force of gravity influences objects in free-fall. If we were to drop a quarter and feather 6’ above the ground theoretically they should fall with the same speed and hit the ground at the same time. We all know that the quarter will hit the ground long before the feather does so how is it possible for both objects to experience the same force and land at the same time? On earth gravity is the force pulling us towards the ground. For objects in free fall the force is equal to acceleration, which on earth is 9.8 m/s2. Using Newton’s laws of motion students will demonstrate the relation between mass, force, and acceleration during free-fall.
Students will learn about Newton’s laws of motion by demonstrating the relationship between mass, force, and acceleration during free-fall.
- Free-fall tube/vacuum tube (see bibliography)
- Masking tape
- Yard stick or measuring tape
- ideo camera & editing software (optional)
- On a wall measure 6’ from the ground and mark every foot with a piece of tape.
- Optional: Setup a video camera to record the free fall. Set the camera up approximately 1.5’ off the ground so it is at about the same plane of the falling objects.
- Take the feather and quarter and drop them from 3’. Which hit the ground first?
- Increase the drop by 1’ each time. What happens to the speed of the quarter and feather as the drop height increases?
- Set up the free fall tube by placing the feather and quarter in the chamber. Seal and remove the air from the tube to create a vacuum.
- Turn the tube so that both the feather and quarter are at rest on the same end. Quickly rotate the tube 180° so the quarter and feather fall to the other end of the tube. Which hit the other end first? What changed we placed the feather and quarter within the tube?
- If you video recorded the experiment you can calculate speed (m/s) by using movie editing software and slowing down playback. Use the tape marks and display clock/timer to determine the speed at each drop height and within the free fall tube.