AST101 Midterm 2

Speed

The amount of travel per time (m/s)

Velocity

Speed and direction of the object

Acceleration

The rate of change of velocity. Can be a change of speed or direction.

What is not an example of acceleration?

A start travels in the galaxy at 156,00km/h

What is Newton’s first law?

An object in motion stays in motion unless it is acted upon by an outside force.

What is Newton’s Second Law?

Acceleration is proportional to force and inversely proportional to mass.

If an object has a greater force acting upon it, what happens to its acceleration?

It increases proportional to the amount of force.

If an object has a great mass what happens to its acceleration?

It is smaller proportional to the size of its mass.

What is Newton’s third law?

For every force there is always an equal and opposite force.

According to Newton’s laws, why would a ball roll to a stop on a flat surface?

The force of friction acts on the ball, causing it to stop.

An astronaut in deep space pushes herself away from her spacecraft, what happens?

She and the spacecraft move apart, with her moving more quickly than the spacecraft.

Momentum

The mass times the velocity, if you add up the momentum of everything in a closed system is conserved.

Angular Momentum

Mass times velocity times distance, in a closed system it is always conserved.

What happens to the angular momentum if the radius of a spinning object increases?

The angular momentum increases.

What is Newton’s universal law of gravitation?

There is a force between any two objects in the universe, force is proportional to the product of the masses of each object, and inversely proportional to the square of the distance.

If you double the mass of the earth, what would happen to its force with the moon?

It would be twice as strong.

If you double the distance between two objects what happens to the force between them?

It decreases by a factor of 4.

What is the acceleration that a falling object will experience due to gravity on Earth?

10m/s

Why would an object fall slower to the ground one the moon rather than the earth?

The earth’s mass is greater, meaning it exerts a larger force on to the objects than the moon.

Free Fall in Orbit

When an object travelling around 26,000 km/h and the force of gravity is canceled out.

Free fall

When the only force acting on an object is the force of gravity

Tidal Locking

When an objects rotational period matches its orbital speed and we only see one side of the planet.

Why is can we only see on side of the Moon?

Due to the larger force that the Earth exerts on the moon than the Moon exerts on the Sun, the moon has stopped moving relative to Earth and is tidally locked.

Why are there tides?

The gravitational attraction between the Earth and the moon applies a force, areas of the Earth closer to the moon have a larger force applied to them, causing them to be pulled towards the moon. Arrears further from the moon have a smaller pull force exerted on them. The varying gravitational force squeezes both the Earth and the Moon causing them to bend. The earth’s rock is too dense to respond to the pull force, but the oceans are less dense and thus respond to tidal forces from the moon. Friction with the rotation earth causes the tides to lag slightly behind the moon, with ‘buldges occurring on either side of the Earth. The lag applies a force on the earth, causing its rotation to continually slow down.

Spring tide

Very strong tides which happen around full and new moons due to the combined tidal forces of the Moon and the Sun on the Earth.

Neap Tide

Very weak tides caused by the Sun partially cancelling the Moon’s tidal forces during the 1st and 3rd quarter moons.

What is hydrostatic equilibrium?

The physical state where the inward pull of gravity inside a fluid or plastic solid is perfectly balanced by the outward push of pressure

If the density of the Sun’s core were to go up, how would equilibrium be maintained?

The rate of fusion would increase causing an increase in temperature and pressure. Due to the increase in pressure the core would expand and its density would drop, restoring the equilibrium.

Nuclear Fission

When two elements combine and break into smaller pieces, emitting nuclear energy.

Nuclear Fusion

When two hydrogen atoms fuse together to create a stronger element, emitting hydrogen and nuclear energy. This is how the power in the sun is generated.

Emission

When light is released from a source

Reflection

When light bounces off something in a straight line

Absorption

When light is not reflected or scattered from an object, black objects absorb all colours.

Transmission

When some or all light is transmitted through a clear or opaque object