Physics: Motion, Forces, and Satellite Orbits Quizlet

Frame of reference

A system for describing motion.

Speed

Distance traveled per unit of time.

Velocity

Speed with direction (a vector).

Acceleration

The rate at which velocity changes (speed, direction, or both).

Newton's 1st Law (Law of Inertia)

An object stays at rest or in uniform motion unless acted on by a net force.

Newton's 2nd Law

Acceleration increases with more force and decreases with more mass.

Newton's 3rd Law (Action-Reaction)

For every action, there is an equal and opposite reaction, acting on different objects.

Inertia

The resistance of an object to a change in motion.

Friction

A force that opposes motion; depends on surface roughness and normal force.

Mass

Amount of matter/inertia, constant everywhere.

Weight

Force of gravity, changes with location.

Gravitational force

If distance doubles, it becomes one-fourth as strong (inverse-square law).

Weight at 1 Earth radius above surface

It becomes one-fourth of what it was on the surface.

Projectile motion

Horizontal velocity stays constant; vertical velocity changes due to gravity.

Dropped ball vs. fired ball

They hit the ground at the same time (ignoring air resistance).

Path of a projectile (no air resistance)

A parabola.

Launch angle for maximum range (no air resistance)

45°.

Complementary angles

Two launch angles that give the same range (add to 90°, like 30° and 60°).

Air resistance effect on projectile motion

Decreases range and height; descent is slower than ascent.

Free fall acceleration

Objects of different mass accelerate the same (g is constant).

Terminal velocity

The maximum falling speed when drag equals weight.

Terminal velocity and mass

Heavier objects reach higher terminal velocity (need more drag to balance their weight).

Work in physics

Force applied over a distance in the direction of motion.

Work-Energy Theorem

Work done equals the change in kinetic energy.

Power

The rate of doing work (work per time).

Energy conservation in falling objects

PE decreases, KE increases, but total energy stays constant.

Mechanical energy

The sum of potential and kinetic energy.

Satellite

A fast-moving projectile that continuously falls around Earth.

Elliptical orbit speed

Speed is greatest at the closest point (perigee).

Elliptical orbit potential energy

Potential energy is greatest at the farthest point (apogee).

Total energy of a satellite in orbit

It stays constant (KE + PE conserved).

Escape velocity

The minimum speed needed to leave Earth's gravity (about 11 km/s).

Weightlessness in orbit

Astronauts feel weightless because they are in continuous free fall around Earth.

Tides on Earth

Caused by the Moon's gravity pulling differently on near and far sides of Earth.

Einstein's theory of gravity

Gravity is the warping of space-time by mass, not just a force.

Equilibrium in forces

Balanced forces, no acceleration.

Scale reading

The normal force (equal to your weight if at rest).

Rope tension

Rope transmits equal force along its length when in equilibrium.

Rocket acceleration in space

By expelling gas backward (action-reaction).

Balloon movement when nozzle released

Air pushes out one way, balloon moves opposite (Newton's 3rd Law).

Breaking different strings with pulls

Slow pull → top string breaks (supports weight). Quick pull → bottom string breaks (mass inertia resists sudden motion).

Doubling mass in Newton's 2nd Law

Acceleration is cut in half for the same force.

Doubling force on the same mass

Acceleration doubles.

Velocity change in free fall

Increases by about 10 m/s each second (on Earth).

Time of flight in projectile motion

Determined by vertical motion (not horizontal speed).

Effect of drag on falling speed

Increases drag → reduces net force → reduces acceleration → eventually reaches terminal velocity.

Conservation of energy in satellites

Total energy (KE + PE) stays constant even as KE and PE trade back and forth.

Gravitational force in elliptical orbit

Strongest at the closest point (perigee) and weakest at the farthest point (apogee).