Unit 1: Forces and Motion Flashcards

Force

A push or pull that can cause an object to change its motion.

Newton (N)

The unit used to measure force.

Net force

The overall force acting on an object after all forces are combined.

Balanced forces

Forces with a net force of 0 N that cause no acceleration.

Unbalanced forces

Forces with a net force greater than 0 N that cause acceleration.

Acceleration

A change in velocity; an object accelerates when it speeds up slows down or changes direction.

Friction

A contact force that opposes motion.

Air resistance

Friction caused by air that opposes the motion of an object moving through air.

Contact force

A force that requires objects to touch.

Noncontact force

A force that can act without objects touching.

Gravity

An attractive noncontact force that pulls objects toward each other.

Magnetism

A noncontact force that can attract or repel magnetic objects.

Electric force

A noncontact force that can attract or repel charged objects.

Newton's First Law

Objects at rest remain at rest and objects in motion remain moving at the same speed and direction unless acted on by an unbalanced force.

Law of Inertia

Another name for Newton's First Law.

Inertia

An object's resistance to a change in motion.

Mass

The amount of matter in an object measured in kilograms.

More mass and inertia

Objects with more mass have more inertia and are harder to start stop or change direction.

Newton's Second Law

An object's acceleration depends on its mass and the force applied.

Newton's Third Law

When one object applies a force to a second object the second object applies an equal and opposite force to the first object.

Action force

The force one object applies to another object in a Newton's 3rd Law force pair.

Reaction force

The equal and opposite force applied back by the second object in a Newton's 3rd Law force pair.

Newton's 3rd Law force pair

Two equal and opposite forces acting on two different objects.

Reference point

An object or location used to determine whether another object is moving.

Speed

How fast an object is moving.

Velocity

Speed in a specific direction.

Acceleration formula

a = (Vf - Vi) / t

Final velocity (Vf)

The velocity of an object at the end of a time interval.

Initial velocity (Vi)

The velocity of an object at the beginning of a time interval.

Speed formula

S = d / t

Distance formula

d = S × t

Time formula

t = d / S

Force formula

F = ma

Acceleration from force and mass

a = F / m

Mass from force and acceleration

m = F / a

Earth's gravitational acceleration

9.8 m/s² toward the center of Earth.

Terminal velocity

The constant velocity reached when upward air resistance equals downward gravity.

Air resistance at terminal velocity

Air resistance equals gravity so net force is 0 and the object stops accelerating.

Surface area and air resistance

Greater surface area generally creates more air resistance and slows falling objects.

Mass and gravitational pull

More mass produces a stronger gravitational pull.

Distance and gravitational pull

Greater distance produces a weaker gravitational pull.

Mass vs. weight

Mass is the amount of matter measured in kilograms while weight is the force of gravity measured in Newtons.

Weight

The force of gravity acting on an object measured in Newtons.

Weight on Earth

Weight = mass × 9.8 m/s².

Converting pounds to kilograms

Kilograms = pounds / 2.2.

Balanced motion

An object with balanced forces can remain at rest or move at constant velocity.

Unbalanced force and acceleration

An unbalanced force causes acceleration which means the object's velocity changes.

Same-direction forces

Add forces that act in the same direction.

Opposite-direction forces

Subtract the smaller force from the larger force and give the direction of the larger force.

More force and acceleration

If mass stays the same more force produces more acceleration.

More mass and acceleration

If force stays the same more mass produces less acceleration.

Rocket action force

The rocket pushes hot gases downward.

Rocket reaction force

The hot gases push upward on the rocket.

Bowling ball and pin action

The bowling ball pushes on the bowling pin.

Bowling ball and pin reaction

The bowling pin pushes back on the bowling ball with an equal and opposite force.

Seatbelt and Newton's First Law

A passenger's body wants to keep moving when a car stops because of inertia; the seatbelt applies a force to stop them.

Penny and notecard experiment

The penny resists changing its motion because of inertia when the notecard is flicked away.

Parachute and air resistance

A parachute increases surface area and air resistance slowing the person's fall.

Terminal velocity sequence

Gravity causes acceleration air resistance increases and eventually air resistance equals gravity causing constant velocity.

Gravity and falling objects

Earth's gravity pulls falling objects toward the center of Earth and causes acceleration of about 9.8 m/s² when air resistance is ignored.

Why balanced forces do not always mean stopped

Balanced forces mean no acceleration so an object can still move at a constant velocity.

Why velocity is a vector

Velocity includes both speed and direction.

Why acceleration is a change in velocity

Acceleration occurs when velocity changes in speed direction or both.

Mass on different planets

Mass stays the same because the amount of matter does not change.

Weight on different planets

Weight can change because the strength of gravity can be different.