Key idea
Universal gravitation
F = G m₁m₂/r²
Masses attract one another. Newton’s law gives an inverse-square force, while the gravitational-field viewpoint describes how a mass changes the space around it for other masses.
Universal gravitation
The key idea
Masses attract one another. Newton’s law gives an inverse-square force, while the gravitational-field viewpoint describes how a mass changes the space around it for other masses.
Why it matters
The same framework connects falling objects, planetary motion and satellites.
A picture to remember
Key idea
Universal gravitation
Guided example
Universal gravitation
Masses attract one another. Newton’s law gives an inverse-square force, while the gravitational-field viewpoint describes how a mass changes the space around it for other masses.
Put it into practice
Universal gravitation
Choose a concrete case linked to Universal gravitation. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.