Unit 3

Does not contain chapters 3.9-onward yet

In what direction does the gravitational force on a system act?

Along a line connecting the two objects

To what is the gravitational force on a system proportional to?

The mass of the system, the object in the surroundings, and (inversely) the square of the distance between the centers of the two objects.

In what direction is the gravitational force on the system due to the surroundings relative to the unit vector r?

In the direction opposite to the unit vector r

Why is the gravitational constant G universal?

Because it is the same for any pair of interacting masses no matter their size or location in the Universe.

How do you calculate gForce?

Find the position of the system relative to the center of the other surrounding object, then find their distance (magnitude), then find the vector force with the known masses

The force that an object in the surroundings exerts on the system is…

equal and opposite to the force that the system exerts on the surroundings. (true for gravitational and electric forces)

If the force that the sun exerts on the Earth is the same, why aren’t they moving with the same velocity?

Because their masses are very different.

In what direction does the Earth’s gravitational field at any point point?

Towards the center of the Earth

Why is the Earth’s gravitational field non-uniform?

Because it consists of layers of non-uniform-density shells (although the difference in their density is in micrometers).

N =

kg * the magnitude of the gravitational field around earth (g) (alternatively, F = mg)

List two similarities between gravitational and electric forces.

The magnitude of both forces is inversely proportional to the square of the distance between the centers of the objects and both forces act along the line connecting the objects

List two differences between the electric and gravitational forces.

Electric charge can be positive or negative while mass is always positive and electric forces can be attractive or repulsive while gravitational forces are always attractive

If both charges have the same sign, then the electric force will be in the direction of _____, while if they have different signs then the force will point in the direction of ______.

the unit vector r, the opposite of r

Why is it reasonable to ignore the gravitational force between two subatomic charges?

Because they have extremely tiny gravitational interactions with each other, making the ratio between the electric force and the gravitational force huge

What kind of matter is usually uncharged (and therefore experiences larger gravitational forces)?

Macroscopic matter

What kind of matter is usually charged and tiny (and therefore experiences larger electric forces)?

Microscopic matter

List some qualities of quarks. They…

Never occur alone, make up hadrons in combination, compose protons (3), neutrons (3), and pions (2), and do not make up leptons (electrons, nutrinos, muons) which are not made up of smaller particles

What is the strong (nuclear) interaction?

An interaction between particles made of quarks that holds the nucleus of an atom together despite the protons repelling each other that is essentially zero unless the particles touch each other and is stronger the larger the nucleus gets

What makes nuclei unstable?

When the strong force is smaller than the electric repulsive force between protons in a nucleus.

Rank the fundamental interactions from strong to weak.

Strong (nuclear), electric, gravitational, weak

What is the weak interaction?

An interaction that occurs during phenomena like beta decay and changes in particle identity and can produce weakly-interactive neutrinos responsible for the instability of a free neutron and its decay and the development of the Standard Model

What is the Standard Model?

A model that describes interactions in terms of the exchange of real or virtual particles, massive or massless, and charged and neutral, rather than in terms of long- or short-range attractions or repulsions.

What is antimatter?

The antiparticle to every particle with equal mass but opposite properties that annihilates its matching particle if they meet and produces other particles (may be produced in nuclear reactions)

What are mesons?

Particles composed of a quark and a different kind of antiquark.

Charge and the number of quarks and leptons is ______ in interactions.

Conserved