Number of g's or g-Forces Introduction

Summary

In this educational transcript, a physics instructor explains the concept of g-forces, both vertical and horizontal, and how they are calculated using simple equations. The class learns about apparent weightlessness, with examples including astronauts in the ISS and scenarios like roller coasters or free-falling elevators. The instructor also shares real-world examples, such as the g-forces experienced by cars, airplanes, and rockets. The key takeaway is that g-forces are ratios comparing an object's acceleration to Earth's gravity, helping students understand how acceleration influences weight perception in different environments.

Takeaways

• 😀 Number of g's (g-forces) is a ratio comparing an object's acceleration to Earth's gravitational acceleration (9.81 m/s²).
• 😀 Vertical g's are calculated as the normal force divided by the force of gravity, while horizontal g's are calculated using acceleration in the x-direction divided by gravitational acceleration.
• 😀 G-forces are not actual forces but ratios that measure how an object’s acceleration compares to the standard gravity on Earth.
• 😀 When at rest, a person experiences 1 vertical g (normal gravity) and 0 horizontal g's.
• 😀 Astronauts in the International Space Station experience apparent weightlessness due to zero net g's, even though gravity still acts on them.
• 😀 Apparent weightlessness occurs when an object experiences zero net g's, which can happen in free-fall or while in specific vehicles or environments.
• 😀 In a free-falling elevator or in space, an object and its occupants experience zero net g's, creating a sensation of weightlessness.
• 😀 To experience apparent weightlessness in a car, the critical speed is when the normal force (force exerted by the ground on the car) is zero, such as going over a hill at high speed.
• 😀 A person in an airplane or roller coaster can also experience apparent weightlessness if the correct speed and trajectory are achieved.
• 😀 Real-life examples of g’s: A Toyota Prius experiences 0.29 horizontal g's, while the Tesla Roadster can achieve 1.4 horizontal g's. Astronauts experience about 3-4 g’s during rocket launches.

Q & A

What is the difference between vertical and horizontal g's?

Vertical g's are calculated by dividing the force normal acting on an object by its weight (force of gravity), while horizontal g's are calculated by dividing the object's acceleration in the x-direction by the acceleration due to gravity.

Why is the number of g's not considered a force?

The number of g's is a ratio of acceleration, not a force. It represents the comparison between the acceleration an object experiences and the acceleration due to gravity on Earth. Therefore, it is dimensionless and has no units.

How do you calculate the vertical number of g's when at rest?

When at rest, the force normal equals the force of gravity. This results in a vertical number of g's equal to 1, as the force normal and force of gravity cancel each other out.

What is apparent weightlessness?

Apparent weightlessness occurs when an object experiences zero net g's, meaning no acceleration in any direction. This can happen in a falling elevator or an orbiting space station, where the object seems weightless even though gravity is still acting on it.

How does the acceleration in the International Space Station compare to that on Earth?

The acceleration due to gravity in the International Space Station is roughly 8.6 m/s², which is about 0.88 vertical g's. This is less than Earth's standard 9.81 m/s².

Why do astronauts experience zero g's in the International Space Station?

Astronauts experience zero g's in the International Space Station because they are in free fall along with the station, creating the effect of weightlessness. There is no force normal acting on them in this situation.

What happens when you experience two vertical g's?

When you experience two vertical g's, it feels as if you weigh twice as much as you normally do on Earth. This happens when the acceleration in the vertical direction is twice that of Earth's gravity.

Can you experience zero net g's outside of space?

Yes, you can experience zero net g's in scenarios such as being in an airplane or roller coaster, or even in a car. For example, driving a car over a hill at the right speed can create a feeling of weightlessness.

What is the relationship between number of g's and weight in a car or airplane?

The number of g's in a car or airplane determines the forces acting on a person, similar to how gravity affects weight. For instance, at certain speeds and positions (like driving over a hill), the forces acting on a person can make them feel weightless or experience more g's than usual.

What is the typical range of g's experienced by astronauts during rocket launches?

During rocket launches, astronauts experience around 3 g's in NASA’s Space Shuttle and about 4 g's in the Russian Soyuz rocket.