Universal gravitational constant

Definition

The universal gravitational constant, denoted as $G$, is a fundamental physical constant that quantifies the strength of the gravitational force between two masses. Its value is approximately $6.674 \times 10^{-11} \text{Nm}^2\text{kg}^{-2}$.

5 Must Know Facts For Your Next Test

1. The universal gravitational constant $G$ appears in Newton's Law of Universal Gravitation: $F = G \frac{m_1 m_2}{r^2}$.
2. $G$ was first measured by Henry Cavendish in 1798 using a torsion balance.
3. The unit of $G$ is $\text{Nm}^2\text{kg}^{-2}$, which ensures that the gravitational force is measured in newtons.
4. $G$ is crucial for calculating gravitational forces not only on Earth but also in celestial mechanics and astrophysics.
5. Despite its importance, $G$ is one of the least precisely known constants in physics due to the difficulty in measuring it accurately.

Review Questions

• What is the numerical value and unit of the universal gravitational constant?
• How does the universal gravitational constant factor into Newton's Law of Universal Gravitation?
• Who first measured the universal gravitational constant and what method did they use?

Related terms

Newton's Law of Universal Gravitation:

A law stating that any two masses attract each other with a force equal to $$F = G \frac{m_1 m_2}{r^2}$$, where $F$ is the force, $G$ is the universal gravitational constant, $m_1$ and $m_2$ are the masses, and $r$ is the distance between their centers.

Gravitational Force:

The attractive force that acts between any two objects with mass; calculated using Newton's Law of Universal Gravitation.

Henry Cavendish: A British scientist who first measured the value of the universal gravitational constant using a torsion balance experiment in 1798.