Magnetism and Magnetic Fields

• A magnet attracts materials like iron and possesses north and south poles, with the poles being the strongest points of the magnet.

Magnetism

• A freely moving magnet will align its poles with the Earth’s north-south axis.
• Cutting a magnet in half results in two magnets, each with its own north and south poles.
• Magnetic force is the force exerted by a magnet on certain materials, including other magnets, over a distance.
• Magnetic force includes both attraction and repulsion.
• North and South poles attract each other; North and North or South and South poles repel.
• Magnets exert force through a magnetic field, the region around a magnetic material or moving electric charge where magnetism acts.
• Magnetic fields interact when magnets are brought close together.

Factors Affecting Field Strength

• Distance, voltage, wraps, and material influence the strength of electric and magnetic fields.
• Increasing the number of wraps around a magnet increases the magnetic field strength, assuming voltage remains constant.
• Increasing the distance from a magnet decreases the magnetic field strength, and vice versa.
• Evidence of fields existing between objects, even without contact, is demonstrated by a compass needle's consistent pointing towards the north or south.
• Substances attracted to magnets, like iron, are pulled or pushed by magnets, further demonstrating the existence of fields.

Velocity and Vectors

• Speed indicates how quickly an object is moving, but not its direction.
• Velocity combines speed and direction, making it a vector quantity.
• Vectors possess both size and direction, often represented by arrows where length indicates speed and direction indicates the object's path.
• Objects moving at the same speed and in the same direction have the same velocity.
• The SI unit for velocity is meters per second (m/s), including directional information.
• Distance equals velocity multiplied by time (D = VT).
• Time equals distance divided by velocity (T = D/V).
• Acceleration due to gravity is approximately 9.8 m/s².

Acceleration

• Acceleration refers to changes in speed and/or direction.
• Acceleration is the rate at which velocity changes and is a vector quantity.
• Experiencing acceleration means feeling a change in velocity, like being pushed into a seat as a car speeds up.
• Negative acceleration occurs when an object moving in a positive direction experiences acceleration in the opposite direction.
• Acceleration only occurs when there is a change in direction, change in speed, or both.

Graphing Motion

• Representing motion through graphs of position vs. time and velocity vs. time help with understanding motion.
• Position vs. Time: Forward movement results in an upward line, backward movement results in a downward line, and staying still results in a stable line.
• Velocity vs. Time: Moving the car forward or faster results in an upward line, the line goes down when the car is being moved in the opposite direction or at a different speed, and a stable line indicates constant velocity.

Calculating Acceleration

• Average acceleration is calculated as the change in velocity divided by the change in time.
• Acceleration is measured in meters per second squared (m/s²).
• Velocity is measured in meters per second (m/s).
• If a biker’s velocity changes from 1 m/s to 6 m/s in 5 seconds, their average acceleration is 1 m/s².
• If a biker’s velocity changes from 6 m/s to 2 m/s in 4 seconds, their average acceleration is -1 m/s².

Newton's Law of Gravity

• Newton’s Law of Universal Gravitation explains that gravity acts between any two masses in the universe.
• The force causing an apple to fall is the same force that causes the moon to orbit the Earth.
• Objects exert equal gravitational pulls on each other.
• The strength of gravity is affected by distance and mass.
• Objects with greater mass have a greater gravitational force between them.
• Objects closer to each other experience a stronger gravitational force.

Acceleration Due to Gravity

• Gravity causes falling objects to accelerate.
• The rate of acceleration due to gravity is 9.8 m/s², meaning velocity increases by 9.8 m/s every second.
• Mass does not affect acceleration due to gravity in a vacuum.
• Objects with greater mass have greater force but also greater inertia, resulting in the same rate of acceleration.
• Wind resistance can cause objects with greater surface area to fall slower.

Inertia

• Inertia is the tendency of an object to resist changes in its state of motion.
• The inertia of an object depends on its mass; greater mass results in greater inertia.
• Inertia must be overcome by an unbalanced force to change an object's motion.
• Friction opposes the motion of objects moving across matter.
• All objects have inertia, regardless of whether they are moving or stationary.
• Newton’s first law of motion is explained by Inertia.

Balanced and Unbalanced Forces

• Balanced forces, such as two figures of equal mass exerting equal force, result in no change in motion.
• The sum of balanced forces is zero.
• Unbalanced forces, such as unequal forces in a rope pull, result in a change of motion.
• Objects move or remain still due to the forces acting upon them.
• Greater mass exerts a greater gravitational force.

Newton's Laws of Motion

• Newton’s 1st Law: An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
• Inertia, the tendency of an object to resist change, is described by this law.
• Newton’s 2nd Law: The acceleration of an object is directly proportional to the net force on the object and inversely proportional to the object's mass (F=MA).

Force, Mass, and Acceleration

• F is force applied to an object, measured in Newtons (N).
• M is the mass of the object, measured in kilograms (kg).
• A is the acceleration, measured in meters per second squared (m/s²).
• The formulas for each variable are: F = MA, M = F/A, A = F/M.
• Increasing force while keeping mass stable increases acceleration.
• Increasing mass while keeping force stable decreases acceleration.

Newton's 3rd Law of Motion

• Every action has an equal and opposite reaction, thus forces act in pairs.
• Newton’s Third Law relates the action and reaction to different objects.
• Unlike balanced forces, action and reaction forces do not cancel out.
• A Reaction Force is when one object exerts a force on another, and that other object exerts the same force in the opposite direction.
• Balanced forces have equal magnitude but in different directions, resulting in no movement or constant movement.
• Gravitational Force is the force of a planet pulling an object to its center.
• Magnetic force is the attraction or repulsion between electrically charged particles.

Momentum

• Momentum is a property of a moving object that makes it hard to stop.
• Momentum equals mass multiplied by velocity (p = mv).
• Greater mass or higher velocity results in greater momentum.
• The SI unit for momentum is kg*m/s.
• The Law of Conservation of Momentum states that in a closed system, momentum is transferred from one object to another, but the total momentum stays the same before and after the collision.

Kinetic Energy

• Kinetic energy is the energy of moving matter.
• Objects with more mass or velocity have more kinetic energy.
• Kinetic energy (KE) is calculated as 1/2 * mass * velocity² (KE = 1/2mv²).
• Velocity affects kinetic energy more than mass because velocity is squared in the equation.

Potential Energy

• Potential energy is energy stored in an object at rest.
• Gravitational potential energy is energy stored in an object above the ground.
• Greater height above the ground results in more gravitational potential energy (GPE = mgh, where g = 9.8 m/s²).
• Elastic potential energy is energy stored in an object's shape when it is stretched or compressed.
• The farther an elastic object is stretched or compressed, the greater its potential energy.

Kinetic and Potential Energy Equations

• Kinetic energy (KE) equals 1/2 * mass * velocity² (KE = 1/2mv²).
• Potential energy (PE) equals mass * gravity * height (PE = mgh, where g = 9.8 m/s²).
• An object in motion has kinetic energy.
• An object at rest has potential energy.

Relationships Between Energy and Speed

• Kinetic energy and speed are directly proportional.
• Potential energy and speed are inversely proportional.
• The height of an object determines its total potential energy.
• Increasing the starting position on a ramp increases total energy.
• Potential energy and kinetic energy are inversely related and can be transformed into each other.

Pendulum Motion

• Only pendulum length and gravity acceleration affect the pendulum period.
• The pendulum period can be calculated using this equation: T=2π√Lg.
• Pullback angle and mass do not affect the pendulum period.

Work

• Work occurs when a force is applied to move an object over a distance, transferring energy.
• Work only occurs if the force applied is moving in the same direction as the object.
• Work (in Joules) equals distance (in meters) multiplied by force (in Newtons): W = FD.
• Work changes the potential energy of an object.

Work Calculations

• Work is calculated using the formula W = FD (Work = Force × Distance).
• Force is calculated using the formula F = W/D (Force = Work / Distance).
• Distance is calculated using the formula D = W/F (Distance = Work / Force).

Mechanical Energy

• Mechanical energy is the sum of kinetic and potential energy (TME = KE + PE).
• Work is done when a force acts on an object causing displacement.
• Kinetic energy is energy due to motion.
• Potential energy is energy due to position, either gravitational or elastic.
• Mechanical energy can do work and apply forces to other objects.
• In some scenarios, total mechanical energy is conserved, while in others, it changes due to external forces.

Mechanical Energy Conservation

• Mechanical energy at the top equals the kinetic energy at the bottom in an isolated system where conservative forces act (GPE(top)=KE(bottom)).
• The law of conservation of mechanical energy states that the total mechanical energy remains constant in such systems.