Newton’s law of universal gravitation

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The Moon’s Centripetal Acceleration

The moon gravitates towards the earth, and by the force of gravity is continually drawn off from a rectilinear motion, and retained in its orbit.

It is solely the gravity of the earth that keeps the moon in orbit.

Slide 10

The Law of Gravitation for Point Masses

Law of universal gravitation- there is a power of gravity pertaining to all bodies, proportional to the several quantities of matter which they contain.

Henry Cavendish (1731-1810)

Hypotheses non fingo

Slide 11

Gravitation for Extended Bodies

Inside a homogeneous hollow spherical shell, a point mass experiences no net gravitational force

Next, if a point mass is placed outside the shell, it is attracted to the exact center as if all of its mass were concentrated at a point

Same for solid sphere of uniform density

Teachers' Domain: String Theory: Newton's Embarrassing Secret

Slide 12

Inertial and Gravitational Masses

Inertial vs. Gravitational mass

Inertial mass vs. weight – “The mass is known by the weight of each body, for it is proportional to the weight, as I have found by experiments on pendulums.”

Kepler’s 3rd Law

Slide 13

A Final Thought

“Nature and nature’s laws lay hid in night; God said ‘Let Newton be!’ and all was light.”