Physics Key Concepts: Force, Motion, Energy, and Variables

Equilibrium

When net force is zero

Net Force

The sum of all forces acting on an object

SI Unit for Force

Newton (N)

SI Unit for Energy

Joule (J)

Graph Title Format

Dependent vs Independent

Slope

Change in y divided by change in x

Distance

Total path traveled

Displacement

Change in position with direction

Speed

How fast something moves

Velocity

Speed with direction

Acceleration

Rate of change of velocity

Free Fall

Motion where gravity is the only force

Acceleration in Free Fall

-9.8 m/s²

Velocity at Highest Point

0 m/s

Scalar

Quantity with only magnitude

Vector

Quantity with magnitude and direction

Newton's First Law

Object stays at rest or in motion unless acted on

Newton's Second Law

F = ma

Newton's Third Law

Every action has an equal and opposite reaction

Normal Force

Force from a surface

Friction

Force that resists motion

Tension

Force in a rope or cable

Weight

Force of gravity on an object

Mass vs Weight

Mass is amount of matter, weight is a force

Force of Gravity

F = mg

Kinetic Friction

fₖ = μₖFₙ

Static Friction

fₛ ≤ μₛFₙ

Projectile Motion

Horizontal and vertical motions are independent

Time Up = Time Down

True for projectiles on level ground

Centripetal Acceleration

a = v²/r

Centripetal Force

Force toward center of circle

Velocity in Circle

v = 2πr/T

Gravitational Force

F = GMm/r²

Momentum

p = mv

Impulse

FΔt

Conservation of Momentum

Total momentum stays the same

Work

W = Fd

Kinetic Energy

K = ½mv²

Gravitational Potential Energy

U = mgh

Elastic Potential Energy

U = ½kx²

Power

P = W/t

Conservation of Energy

Energy cannot be created or destroyed

Mechanical Advantage

MA = Fᵣ/Fₑ

Independent variable

The variable you change or control in an experiment; it goes on the x-axis

Dependent variable

The variable you measure; it changes because of the independent variable and goes on the y-axis

Elastic Collision

Both momentum and kinetic energy are conserved

Inelastic Collision

Momentum is conserved, energy is not

Centripetal Direction

Always toward the center of the circle

Perfect Elastic Collision

A type of collision where kinetic energy is conserved, and the objects bounce off each other without any loss of energy.

Perfect Inelastic Collision

A type of collision where kinetic energy is not conserved, and the objects stick together after the collision.

Momentum

mass in motion, kg times m/s

Impulse

the result of force acting on an object for some distance, changing the object's energy, kg times m/s

Work

the result of force acting on an object for some distnace, changing the object's energy, J

Power

The rate at which work is done, Watts