PY 131 Chapter 9: Gravity

What is Newtonian Synthesis?

The unification of the physics governing the celestial and terrestrial.

What was the consequence of Newtonian Synthesis?

One of its consequences was the American Revolution.

What did Newton try to find to explain the motion of objects?

One 'Law of Gravity'.

What did Kepler's laws of planetary motion state?

The path of each planet around the Sun is an ellipse with the Sun at one focus, an imaginary line drawn from each planet to the Sun sweeps out equal areas in equal times, and the square of a planet's orbital period is proportional to the cube of its mean distance from the Sun.

What is Newton's Law of Universal Gravitation?

Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them.

What is the constant called that is used in the mathematical form of Newton's Law of Universal Gravitation?

Newton's Gravitational Constant, or Big G.

What is the mathematical form of Newton's Law of Universal Gravitation?

F_21 = F_12 = G(m1m2/d^2)

What is the force exerted by a uniform spherical shell upon a point object inside the shell?

Zero

What does the distance 'd' represent in Newton's Law of Universal Gravitation?

The distance between the two objects.

What did Cavendish's experiment prove?

Newton's law experimentally on Earth.

What did the measurement of G by Cavendish allow us to find?

The mass of the Earth.

What changes the measured value of 'g' over the surface of the Earth?

The Earth's rotation.

What is the net force on an object at the Equator?

Zero.

What was the force that causes an apple to accelerate as it falls?

The force of gravity.

What is the force that holds the Moon to the Earth?

The force of gravity.

What does Newton's 3rd Law tell us about the force of gravity?

The force of gravity is equal and opposite for each object.

What is the assumption that Newton tried and used in deriving Kepler's three laws?

The force of gravity decreases as the square of the distance between the two objects.

What allows us to use Newton's Law of Gravitation for spherical objects?

The force exerted by a sphere on a point object outside the sphere acts as if all the mass of the sphere were concentrated at its center.

What is sometimes called Action At A Distance?

Gravity.

What would happen to the Earth's gravitational attraction to the Sun if the Sun collapsed and became a black hole with the same mass?

It would be the same as before.