MS-PS3-2: Potential Energy Systems

MS-PS3-2
Potential Energy Systems

Middle School

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Learning Objectives

• Model how an object's position affects potential energy in different fields.

• Describe how forces transfer energy, changing an object's potential or kinetic energy.

• Explain that potential energy is stored in a system of interacting objects.

• Analyze how magnetic and electric forces act at a distance through fields.

Key Vocabulary

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System

A system is a group of interacting or interdependent objects forming a complex whole.

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Potential Energy

Potential energy is the stored energy an object has due to its position or state.

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Kinetic Energy

Kinetic energy is the energy that an object possesses due to its motion.

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Net Force

The net force is the overall force acting on an object when all individual forces are combined.

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Magnetic Field

A magnetic field is an area around a magnet where its magnetic force can be detected.

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Electric Field

An electric field is a region around a charged particle where an electric force is exerted.

Key Vocabulary

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Electric Charge

Electric charge is a basic property of matter that can be either positive or negative.

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Electric Current

The rate at which electric charge flows through a conductor, measured in amperes, and powers our electronic devices.

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Friction

Friction is a force that opposes the motion between two surfaces that are in contact.

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Induced Magnetism

The process by which a material becomes temporarily magnetized when placed near a magnet.

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Understanding Net Force

Balanced Forces

• When the net force is zero, all forces are balanced, and the object’s motion does not change.

• The force of gravity pulling a laptop down is matched by the upward push of the table.

• The net force is zero, so the forces are balanced and the laptop does not move.

Unbalanced Forces

• If the net force is not zero, the forces are unbalanced, causing the object's motion to change.

• For instance, a breeze moves paper when its force is greater than the force of friction.

• Even a tiny net force will cause an object to accelerate, meaning it changes its motion.

Multiple Choice

What is required to cause a change in an object's motion?

• An unbalanced net force

• A balanced net force

• The object's total mass

• The absence of all forces

Multiple Choice

When all the forces acting on an object are balanced, what can be concluded?

• The net force on the object is zero.

• The object has no forces acting on it.

• The force of gravity is the only force acting on it.

• The object is accelerating.

Multiple Choice

A piece of paper sitting on a desk is moved by a slight breeze. Which statement provides the best explanation for why the paper moves?

• The force of the breeze is greater than the force of friction, resulting in an unbalanced force.

• The force of the breeze and the force of friction are equal, resulting in a balanced force.

• The force of friction is greater than the force of the breeze, keeping the paper still.

• The net force on the paper is zero, allowing it to move.

Potential Energy in a System

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Gravitational Field

• ​Energy is stored in the Earth-ball system when the ball is lifted.

• ​​Applying a force to lift the ball transfers energy to the system.

• ​The higher the ball is lifted, the more potential energy is stored.

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Magnetic Field

• ​Potential energy is stored between two interacting magnets in a magnetic field.

• ​​A force is needed to pull attracting magnets apart or push repelling ones.

• ​This work stores potential energy in the system.

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Electric Field

• ​Energy is stored in the electric field between a balloon and hair.

• ​​Work is done pulling a negatively charged balloon from positively charged hair.

• ​This action stores potential energy in the system's electric field.

Multiple Choice

What fundamental action is required to store potential energy in a gravitational, magnetic, or electric system?

• Applying a force that changes the position of objects within a field.

• Increasing the speed at which the objects are moving.

• Decreasing the mass of the objects in the system.

• Making the objects hotter or colder.

Multiple Choice

What do the actions of lifting a ball, pulling attracting magnets apart, and separating a charged balloon from hair have in common?

• Each action involves doing work against a force to store potential energy.

• Each action is an example of converting potential energy into motion.

• Each action can only happen within a gravitational field.

• Each action permanently increases the energy of the objects themselves.

Multiple Choice

A student lifts an identical book from the floor to a low shelf and from the floor to a high shelf. Based on the principles of energy storage, which statement is correct?

• More potential energy is stored in the Earth-book system when the book is on the high shelf.

• More potential energy is stored in the Earth-book system when the book is on the low shelf.

• The amount of potential energy stored is the same for both shelves.

• No potential energy is stored in either system because the books are not moving.

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Magnetic Forces

• A magnetic field is an invisible area of force around a magnet.

• Like poles repel each other, while opposite poles attract each other.

• A magnet can make an iron object a temporary magnet, causing attraction.

• Moving magnets against their force stores potential energy in the field.

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Multiple Choice

What is a magnetic field?

• An invisible area of force surrounding a magnet.

• The visible light pattern shown by iron filings.

• The energy stored inside a stationary magnet.

• A temporary charge on an iron object.

Multiple Choice

What is the relationship between the poles of two magnets and the force they exert on each other?

• Like poles create a repulsive force, while opposite poles create an attractive force.

• Both like and opposite poles create a repulsive force.

• Both like and opposite poles create an attractive force.

• The distance between poles determines attraction, not the type of pole.

Multiple Choice

If you use one magnet to push another magnet away without them touching, and then hold it there, what happens as a result of working against their repulsive force?

• Potential energy is stored in the magnetic field.

• The iron nail becomes a permanent magnet.

• The attractive force becomes a repulsive force.

• The magnetic field between them is destroyed.

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Electric Charge

• Electric charge is a property of matter; opposite charges attract and like charges repel.

• ​Static electricity is a charge that isn't moving, like a balloon on hair.

• Pulling attracted objects apart increases the system's stored potential energy.

• Electric current is moving charge that needs a complete path, called a circuit.

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Multiple Choice

What is the fundamental principle that describes how electric charges interact?

• Opposite charges attract, and like charges repel.

• All electric charges repel each other.

• All electric charges attract each other.

• Electric charges have no effect on one another.

Multiple Choice

What is the key difference between static electricity and an electric current?

• Static electricity is a stationary charge, while an electric current is a moving charge.

• Static electricity requires a complete circuit, while an electric current does not.

• An electric current is a form of potential energy, while static electricity is not.

• An electric current involves attraction, while static electricity involves repulsion.

Multiple Choice

Based on the principles of electric forces, what would happen to the stored potential energy in a system if two balloons with opposite charges were pulled farther apart?

• The potential energy in the system increases because work is done against the attractive electric force.

• The potential energy in the system decreases because the objects are getting farther apart.

• The potential energy becomes zero because the attractive force disappears.

• The electric current in the system increases as the objects are pulled apart.

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What Is Electromagnetism?

• An electric current flowing through a wire creates a surrounding magnetic field.

• An electromagnet is a wire coiled around a core, creating a temporary magnet.

• Increase coil count or current to make the electromagnet more powerful.

• Superconducting magnets are used in MRI machines and Maglev trains.

Multiple Choice

What is the direct result of an electric current flowing through a wire?

• A magnetic field is created around the wire.

• The wire begins to glow brightly.

• The wire becomes permanently magnetized.

• The electrical current is converted to sound.

Multiple Choice

How can you increase the strength of an electromagnet?

• Increase the electric current or add more coils.

• Use a shorter wire and a smaller core.

• Decrease the electric current or remove coils.

• Reverse the direction of the electric current.

Multiple Choice

An engineer needs to design a powerful superconducting magnet for an MRI machine. Which combination of factors would produce the strongest possible electromagnet?

• Using a very high electric current and a large number of coils.

• Using a low electric current and a small number of coils.

• Using a high electric current with only a few coils.

• Using a large number of coils with a low electric current.

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Energy Transfer: Potential to Kinetic

• Potential energy is stored energy, while kinetic energy is the energy of motion.

• A marble on a ramp converts potential to kinetic energy as it rolls down.

• Greater mass or a higher start means more potential and kinetic energy.

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Multiple Choice

Which statement correctly defines potential and kinetic energy?

• Potential energy is stored energy, while kinetic energy is the energy of motion.

• Kinetic energy is stored energy, while potential energy is the energy of motion.

• Potential energy and kinetic energy are both forms of stored energy.

• Potential energy and kinetic energy are both forms of the energy of motion.

Multiple Choice

What happens to a marble's energy as it rolls down a ramp?

• Its potential energy is converted into kinetic energy.

• Its kinetic energy is converted into potential energy.

• It creates new energy as it moves.

• It loses all its energy to the ramp.

Multiple Choice

Two marbles of the same mass are placed at the top of two different ramps. If one marble starts from a higher point than the other, what can be predicted about their energy?

• The marble starting from the higher point will have more kinetic energy at the bottom.

• The marble starting from the lower point will have more kinetic energy at the bottom.

• Both marbles will have the same kinetic energy at the bottom.

• Only the marble with greater mass will have kinetic energy.

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Energy Transfer and Friction

Energy Transfer

• Energy is transferred from one object to another during a collision.

• When a moving marble hits a cube, its kinetic energy is passed to the cube.

• This energy transfer causes the stationary cube to move and the marble to slow down.

Effects of Friction

• Friction is a force that resists motion and causes the cube to slow down.

• The force of friction converts the cube's kinetic energy into thermal energy or heat.

• This energy transformation slightly warms both the cube and the surface it slides on.

Multiple Choice

What happens to energy when a moving object, like a marble, collides with a stationary object, like a cube?

• Energy is transferred from the moving object to the stationary object.

• The total energy of the system increases.

• The kinetic energy is destroyed completely.

• Energy is created at the moment of impact.

Multiple Choice

What is the relationship between friction and the kinetic energy of a sliding cube?

• It resists the cube's motion and converts its kinetic energy to heat.

• It pushes the cube forward, making it accelerate.

• It makes the surface colder as the cube slides.

• It increases the amount of kinetic energy the cube has.

Multiple Choice

After a moving marble hits a stationary cube, the cube slides for a short distance and stops. Which statement best explains why the cube and the surface are slightly warmer after it stops?

• The cube's kinetic energy was converted into thermal energy by friction.

• The initial impact of the marble created all the heat.

• The cube released cold energy as it slowed down.

• The air around the cube heated it up as it moved.

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Common Misconceptions

Misconception	Correction
Potential energy is a property of a single object.	Potential energy is stored in a system of interacting objects.
A stationary object has no forces acting on it.	A stationary object has balanced forces, resulting in a net force of zero.
When a sliding object stops, its energy is lost.	Energy is transferred; friction converts kinetic energy into thermal energy.

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Summary

• Potential energy depends on position and is conserved as it changes forms.

• A non-zero net force is required to change an object's motion.

• Forces like magnetism and electricity act at a distance through fields.

• Opposite poles attract, while like poles repel; electric currents create magnetic fields.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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