Physics

Front: Shape of planetary orbits? (Keplers 1st)

Planets move in elliptical orbits with the Sun at one focus.

Equal areas law? (Keplers 2nd)

A line from a planet to the Sun sweeps equal areas in equal times → planets move faster when closer to the Sun.

Kepler’s 3rd Law: Relationship between distance and period?

P² = D³ (P in Earth years, D in AU). Farther planets take longer to orbit.

Point in orbit where a planet is closest to the Sun

Perihelion

Aphelion: Farthest point from the Sun?

Aphelion

Orbital Period

Time it takes a planet to complete one full orbit (usually in Earth years).

Gravity

An attractive force between any two masses; weakest fundamental force but acts over long distances.

Law of Universal Gravitation: How do masses attract?

Force depends on both masses and distance² between centers.

Big G

Universal gravitational constant or 6.67 × 10⁻¹¹ N·m²/kg². It just is the universal constant.

Weightlessness

Not real

Apparent Weightlessness: Why do astronauts feel weightless?

They are in freefall, so no normal force is felt.

Microgravity

Another term for apparent weightlessness, NOT weak gravity.

Inertia

Resistance to changes in motion; depends on mass.

Force

Any push or pull. Newtons (N)

Net Force

Vector sum of all forces acting on an object.

Static Friction: When does static friction act?

Prevents motion when an object is at rest.

Kinetic Friction: When does kinetic friction act?

Acts when surfaces are moving past each other.

Types of Kinetic Friction

Sliding, rolling, fluid.

Fundamental Forces

Gravity, Strong Nuclear, Weak Nuclear, Electromagnetic.

Force Field: What is a force field?

Region where a force can affect other objects.

Mass

Amount of matter; scalar; always positive.kg

Weight

Force of gravity on mass; vector. N

Newton’s 1st Law

Objects stay at rest or in motion unless acted on by a net external force.

Newton’s 2nd Law: Force–mass–acceleration relationship?

Acceleration increases with force and decreases with mass. a= Fnet/m

Newton’s 3rd Law: Action–reaction law?

Forces come in equal and opposite pairs on different objects.

Speed

Distance traveled per time; scaled s = d / t Unit: m/s

Velocity

Speed with direction; vector. v = Δx / t

Average Speed

Total distance ÷ total time.

Instantaneous Speed

Speed at a specific moment.

Acceleration

Rate of change of velocity. a = (vᶠ − vᶦ)/t Unit: m/s²

Distance

Total path length; scaled m

Displacement

Straight-line change in position; vector.