Last week's treasure hunt had a question about dropping different objects from the same height to find which one hit the ground first. We had a lot of emails about this particular activity. This week we explore this question further to find out if heavier objects fall faster than lighter ones.
You will need
two objects of similar size, but different mass (in this activity we used a cricket ball and a tennis ball)
a ladder, step stool or something to drop your objects from like a balcony
What to do
Climb the ladder or drop site and prepare to drop both balls from the same height at the same time.
Drop the balls. Which ball hit the ground first? Did they hit at the same time?
Now drop the hammer and feather from the same height. Which one hit the ground first?
You will find that both objects land at the same time. Why is this? It's because all objects fall at the same rate, regardless of their mass - a concept known as the law of falling bodies. Try this activity with other objects. The objects don't have to be the same size. The objects will reach the ground at very similar times and if you removed air resistance, they would reach the ground at exactly the same time.
When you drop the hammer and the feather air resistance had a significant effect on the feather, slowing it down considerably. If you removed air resistance the hammer and the feather will hit the ground at the same time. How could we test this to see what would happen?
How fast something falls isn't dependant on the mass of the object. Acceleration due to gravity is a constant regardless of the mass of the object. The force at which the object hits the ground is dependant on the mass but not how fast those objects fall, as this is a constant – gravity causes the same acceleration for everything.
The first person to explore this was Galileo Galilei in the The Falling Bodies Experiment. Although it is disputed as historical fact, it is widely believed he dropped two objects from the Leaning Tower of Pisa to prove his theory.
Some terms to consider
Mass is the amount of matter in a given volume of something.
Volume is the amount of space that an object or substance takes up.
Gravity is the force that exists between any two objects that have mass.
Weight is a measure of the force of gravity pulling on an object.
Galileo Galilei (1564 – 1642) was an Italian physicist , astronomer, astrologer, and philosopher closely associated with the scientific revolution. One of his most famous experiments was his demonstration from the Leaning Tower of Pisa.
In the late 16th century, it was generally believed heavier objects would fall faster than lighter objects; Galileo thought differently. He hypothesized that two objects would fall at the same rate regardless of their mass. Legend has it that in 1590 he climbed the Leaning Tower of Pisa and dropped several large objects from the top. The objects did reach the ground at very similar times and Galileo concluded if you removed air resistance, they would reach the ground at exactly the same time.
If you were a scientist during the time of Galileo your ideas were often based on observation and thought alone. Some say Galileo's greatest contribution to science was the popularisation of experiments, as opposed to pure thought, as the primary means for understanding the natural world.
Another fascinating side to this legend is that it was a public demonstration that allowed others to understand his idea. After Galileo's death, other scientists continued to do similar demonstrations to explain their ideas. The popularity of such demonstrations continues to this day, featuring in many hands-on science exhibits.
It is debatable whether Galileo's famous experiment on falling bodies from the Leaning Tower of Pisa actually occurred. Nor was he first to suggest this theory. As far back as the sixth century, other scholars experimented with falling bodies and concluded the general belief was wrong.
So what if there was no original experiment? Galileo inspired an entire genre of experiments and demonstrations that allow us to change how we think and see.
The Apollo "feather-drop" was not the most accurate science experiment. No one measured the height from which the objects were released nor the time they took to fall and Scott was leaning over with his arms not parallel to the ground. But as a demonstration it is unforgettable and so too is Galileo.
Any two objects that are similar in size but have a different mass will work for this activity.
It will be hard to drop the two objects from exactly the same height at exactly the same time.
You will need to have someone watching to record when the objects fall.
Now try dropping a feather and a hammer. Which one hits the ground first?
The Apollo "feather-drop" was not the most accurate science experiment. No one measured the height from which the objects were released nor the time they took to fall and Scott was leaning over with his arms not parallel to the ground. But as a demonstration it is unforgettable and so too is Galileo. Image: NASA