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Chapter 4: Problem 56

Go to NASA's "Apollo 15 Hammer-Feather Drop" Web page (http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_15_ feather_drop.html) and watch the video from Apollo 15 of astronaut David Scott dropping the hammer and falcon feather on the Moon. (You might find a better version on YouTube.) What did this experiment show? What would happen if you tried this on Earth with a feather and a hammer? Would it work? What would you see? Suppose instead you dropped the hammer and a big nail. How would they fall? How fast do things fall on the Moon compared to on Earth?

Short Answer

Expert verified
The experiment showed that without air resistance, objects fall at the same rate. On Earth, air resistance causes a feather to fall slower than a hammer. The hammer and nail would fall at the same rate on both the Moon and Earth due to minimal air resistance.

Step by step solution

01

- Watch the Video

Go to NASA's 'Apollo 15 Hammer-Feather Drop' webpage or find the video on YouTube. Watch astronaut David Scott drop a hammer and a feather simultaneously on the Moon.
02

- Observe the Result

Notice that both the hammer and the feather fall at the same rate and hit the lunar surface at the same time. This demonstrates the concept of gravitational acceleration.
03

- Compare with Earth

If you performed the same experiment on Earth, the feather would fall much slower than the hammer because of air resistance. The hammer, being denser, would fall faster due to less air resistance.
04

- Hammer and Nail on Earth

Dropping a hammer and a big nail on Earth would result in both objects falling at nearly the same rate because air resistance is negligible for such dense objects, showing similar behavior to the Moon experiment.
05

- Gravitational Acceleration on the Moon and Earth

Gravitational acceleration on the Moon is about 1/6th that of Earth. This means objects fall slower on the Moon than on Earth, yet without air resistance on the Moon, all objects fall at the same rate regardless of their mass.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Apollo 15 Experiment
The Apollo 15 experiment, conducted by astronaut David Scott, is a famous demonstration in the field of physics. During one of the Apollo 15 missions to the Moon, Scott dropped a hammer and a feather simultaneously. On Earth, this would result in the feather falling much slower due to air resistance. But on the Moon, both the hammer and the feather hit the ground simultaneously. This outcome shows that in the absence of air resistance, all objects fall at the same rate, regardless of their mass. The experiment beautifully highlights the principle of gravitational acceleration and how different conditions, like those on the Moon, can impact the way objects move.
Air Resistance
Air resistance is a form of friction that acts on objects as they travel through the air. Heavier and denser objects, like a hammer, tend to be less affected by air resistance and fall faster compared to lighter objects, such as feathers, that experience more drag. On Earth, this means objects with different shapes and masses will fall at different rates if dropped from the same height. However, air resistance does not play a role on the Moon because it lacks an atmosphere. This absence allows us to observe pure gravitational acceleration, as demonstrated in the Apollo 15 experiment where the feather and hammer fall at the same rate.
Gravity on the Moon
Gravity on the Moon is much weaker than on Earth, being approximately 1/6th as strong. This difference in gravitational pull means that objects on the Moon will fall more slowly than they do on Earth. The Moon's weaker gravity is due to its smaller mass and size compared to Earth. Despite the slower fall, the lack of atmosphere means there is no air resistance, resulting in all objects regardless of their mass falling at the same rate. The Apollo 15 hammer-feather drop clearly shows how the same principles of physics we observe on Earth can yield varied outcomes when tested in environments with different gravitational forces.
Gravity on Earth
On Earth, gravity is stronger, causing objects to accelerate downwards at around 9.8 m/s². When you drop two objects of different masses, like a hammer and a feather, in a vacuum (an environment without air), they fall at the same rate due to gravitational acceleration. However, in the presence of air, the feather faces much greater air resistance than the hammer, leading it to fall more slowly. When performing the same experiment with a hammer and a nail, since both objects are dense and have relatively low surface area relative to their mass, they experience minimal air resistance and fall at nearly the same rate, similar to the conditions observed on the Moon.

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