Teacher resources and professional development across the curriculum

Teacher professional development and classroom resources across the curriculum

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Related Resources

Free Fall and Air Resistance

Describes the law of acceleration, with illustrations and animation.

Falling Bodies
Explains the force of gravity and how it affects falling bodies.

Weightless Water Trick

If you want to observe the free-fall phenomenon in action, try the following demonstration in your home.

  • Find a plastic or paper cup.
  • Drill or punch two holes (approximately one-quarter inch in diameter) on opposite sides of the cup .
  • Fill the cup to the rim with water. The water will flow from the cup through the holes.
  • Now refill the cup, cover the holes with your fingers, and drop the cup from an elevated position. The water won't flow out of the holes during this free fall.

What makes it work?
When the cup is at rest, the force of gravity pulls downward upon the water. At the location of the holes, there is nothing to balance gravity's force and prevent water from spilling out of the cup.

However, when the cup is in free fall, the water will not leak, making it seem as though the water is not experiencing the downward pull of gravity. It is merely falling to the ground at the same rate as its surroundings (the cup).

This feeling of weightlessness (the sensation that you are not experiencing the downward pull of gravity) is also experienced by riders on free-fall rides. On the way to the top, the riders are pressed against their seats, which provides a sense of weight. But as they free fall, they fall at the same rate as their surroundings-in this case, their seats. Without the force of their surroundings pressing on them, the riders feel like they are weightless. But, in fact, they do have weight and are being acted upon by the force of gravity.

[Back to Free Fall]    [Next: Pendulum]


"Amusement Park Physics" is inspired by programs from The Mechanical Universe...and Beyond.


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