Falling Objects Revisited

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Updated on Feb 08, 2012

Grade Level: 4th - 8th; Type: Physical Science

To discover whether there are some objects that do not fall at a constant rate.

The purpose of this experiment is to test various objects to determine whether they fall at the same rate.

• What does Newton’s second law of motion state?
• How did Galileo discover that objects fall at the same rate?
• Why did Galileo stipulate that objects fall at the same rate in a vacuum?
• What role does air resistance play in the downward acceleration of an object?
• What is terminal velocity?

400 years ago, the famous physist Galileo discovered that falling objects accelerate at the same rate of speed. It does not matter whether you drop a penny or a shot put out a third story window, the two objects will fall at the same rate and reach the ground at the same time. This constant acceleration was later discovered to be the force of gravity. Though his theory was correct, not all objects will fall at the same rate because gravity is not the only force acting on them. Air resistance and lift create forces that push a falling object away from the center of the Earth’s gravity, slowing the speed of descent.

• Various objects that can be dropped out of a second or third story window. Include a feather and a piece of paper in the objects.
• A friend to make observations at the bottom.
• A notebook
• A pencil

e:

1. Find a friend who can help you make observations and drop objects out of windows.
2. Collect an assortment of different objects that you will drop. Make sure you have a feather and a piece of paper among the objects. Make sure it is okay to break any of the objects that you drop.
3. Find a second or third story window that you can drop objects out of.
4. Go up to the window with all the objects. Your friend stays on the ground and observes from a safe distance.
5. Hold one object in each hand.
6. Announce to your friend which objects you are testing.
7. You friend should write the names of these objects in a notebook.
8. Drop the objects out the window at exactly the same time. It is important that you simply drop them; do not throw them out the window as this will add force that you cannot account for in the experiment.
9. Your friend observes and records whether one object landed first or both landed at the same time.
10. Repeat steps 5-9 until you have dropped all the objects out the window.
11. Reverse roles with your friend and repeat the experiment.

Terms/Concepts: Gravity; Free fall; Weight; Mass; Force; Constanct speed; Air resistance; Lift; Acceleration; Center of gravity; Newton’s second law of motion; Vacuum; Terminal velocity

References:

Writer and educator Crystal Beran is rarely seen without a pen. Her adventures have brought her to four continents and her quest for answers has led her to discover more questions than she could fill all the pages with. She currently resides in Northern California, where she can be found sipping tea and writing books.