# How tall is this building? | Summary and Q&A

281.8K views
December 1, 2016
by
Physics Girl
How tall is this building?

## TL;DR

Exploring the physics of tall buildings and how a penny dropped from the top of a building could go into orbit.

## Key Insights

• 🥳 The Earth's rotation affects the linear speed of different parts of tall buildings.
• 🛰️ The centrifugal force can counteract the force of gravity, creating an artificial gravity effect.
• 👻 There is a height above Earth's surface where the centrifugal force balances the gravitational force, allowing objects to go into orbit.

## Transcript

[MUSIC PLAYING] Hello! I'm Diana, and you're watching "Physics, Girl!" So the idea for this video came from a conversation with a friend where we were talking about tall buildings, because Earth is spinning, and tall buildings are spinning around with it especially fast at the equator from the perspective of someone looking down at Earth. So you c... Read More

### Q: How does the Earth's rotation affect the linear speed of different parts of tall buildings?

The Earth's rotation causes different parts of tall buildings to move at different linear speeds. The further away a part is from the Earth's axis of rotation, the faster it moves linearly.

### Q: How does the centrifugal force counteract the force of gravity in a spinning building?

The centrifugal force in a spinning building counteracts the force of gravity, creating a fake force of artificial gravity that pulls away from Earth. This fake force feels like the opposite of gravity.

### Q: At what height would a penny dropped from the top of a building go into orbit?

The penny would have to be dropped from a height approximately 35,786 kilometers above Earth's surface in order to go into orbit.

### Q: Can buildings be constructed to reach such great heights?

Building heights similar to the one required for a penny to go into orbit are unlikely in reality. Future technologies, such as carbon nanotubes, may be required to construct buildings of such heights.

## Summary & Key Takeaways

• The Earth's rotation causes different parts of tall buildings to move at different linear speeds.

• If a building was tall enough, a penny dropped from the top could go into orbit due to the centrifugal force balancing the gravitational force.

• The height required for the penny to go into orbit is approximately 35,786 kilometers above Earth's surface.