MS-PS2-1: Newton's Third Law

MS-PS2-1
Newton's Third Law

Middle School

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Learning Objectives

• Define and describe all three of Newton's laws of motion.

• Apply Newton's laws to explain the motion of objects that have collided.

• Use Newton's Third Law to design a solution to a collision problem.

• Explain how engineering solutions, like helmets or airbags, protect the brain by applying Newton’s Third Law.

Key Vocabulary

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Newton's First Law

An object at rest tends to stay at rest, and an object in motion continues moving.

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Newton's Second Law

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Newton's Third Law

This law explains that for every action, there is an equal and opposite reaction force.

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Force

A force is simply a push or a pull on an object from another object's interaction.

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Collision

A collision happens when two or more objects exert forces on each other over a short time.

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System

In physics, a system is a specific group of interacting objects or components being studied.

Key Vocabulary

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Criteria

The requirements a design solution must meet to be successful.

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Constraints

Limitations on a design, such as cost, materials, or time.

Newton's Three Laws of Motion

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Law 1: Law of Inertia

• An object at rest will stay at rest unless a force acts on it.

• An object in motion will stay in motion at the same speed and direction.

• Inertia is an object's resistance to changing its state of motion.

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Law 2: Law of Acceleration

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Law 3: Action-Reaction

• For every action, there is an equal and opposite reaction.

• Forces on interacting objects will always occur in pairs.

• The forces are equal in strength and opposite in direction.

Multiple Choice

What fundamental concept do Newton's Three Laws of Motion explain?

• The relationship between force and an object's motion

• The relationship between an object's mass and its volume

• The relationship between an object's energy and its temperature

• The relationship between gravity and an object's weight

Multiple Choice

According to the Law of Acceleration, if the same net force is applied to two objects, one with a large mass and one with a small mass, what will happen?

• The object with less mass will accelerate more.

• The object with more mass will accelerate more.

• Both objects will accelerate at the same rate.

• Neither object will accelerate.

Multiple Choice

When air rushes out of a balloon, the balloon moves in the opposite direction. Which law explains this?

• Newton’s First Law

• Newton’s Second Law

• Newton’s Third Law

• Law of Gravitation

Applying Newton's Laws: Basketball

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Law 1: Inertia

• A basketball will stay at rest until a player passes it.

• A moving ball travels straight until an outside force acts on it.

• Gravity is an outside force that pulls the basketball downwards.

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Law 2: F=ma

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Law 3: Action-Reaction

• When a player dribbles, the ball pushes down on the floor.

• The floor pushes the ball up with an equal and opposite force.

• When jumping, the player pushes down and the floor pushes them up.

Multiple Choice

Which principle explains why a basketball remains at rest on the court until a player picks it up and passes it?

• The Law of Inertia

• The Law of F=ma

• The Law of Action-Reaction

• The Law of Gravity

Multiple Choice

Based on Newton's Second Law $$F=ma$$ , why must a player use more force to shoot a heavier basketball than a lighter one?

• A heavier basketball has more mass, requiring greater force to accelerate at the same rate.

• A heavier basketball is affected more by the force of gravity when thrown.

• The floor pushes back with less force on a heavier basketball.

• Inertia causes a heavier basketball to move faster than a lighter one.

Multiple Choice

A player jumps to take a shot. Which statement best analyzes this action using the principles of Newton's Third Law?

• The player pushes down on the floor, and the floor pushes the player up with an equal and opposite force.

• The player's acceleration is determined by their mass and the force of their jump alone.

• The player's inertia allows them to overcome the force of gravity temporarily.

• The force from the player's jump is transferred to the ball, making it go higher.

Designing Solutions for Collisions

• Engineers use Newton's Third Law to design solutions for collisions.

• Designs account for equal and opposite reaction forces during a crash.

• Technologies like airbags and crumple zones help reduce impact forces.

• Crumple zones absorb and spread out the force of a collision, reducing the impact on passengers by managing the equal and opposite reaction forces.

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Multiple Choice

What scientific principle do engineers use as the basis for designing solutions to manage collisions?

• Newton's Third Law

• The Law of Universal Gravitation

• The Law of Conservation of Energy

• The Theory of Relativity

Multiple Choice

What is the primary function of technologies like airbags and crumple zones in a vehicle?

• To make the car heavier

• To increase the speed of the collision

• To reduce the impact forces on the occupants

• To prevent the car from making noise

Multiple Choice

Considering the principle of equal and opposite reaction forces, which statement best explains how crumple zones protect passengers?

• They help the car bounce off the other object with more force.

• They make the car rigid to prevent any damage.

• They are designed to absorb and redirect the reaction forces away from passengers.

• They cancel out the opposing force so that it disappears.

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Design Criteria and Constraints

Criteria

• Criteria are the goals or requirements that a successful design must meet to be successful.

• For a bicycle helmet, this includes a high level of impact protection for the wearer.

• Other criteria include the helmet being lightweight and fitting securely on the rider's head.

Constraints

• Constraints are the limitations or challenges that must be considered during the design process.

• These can include the cost of materials and the final mass of the product.

• Time for development and limits of current technology are also common types of constraints.

Multiple Choice

Which of the following is a design constraint for a bicycle helmet?

• Fit securely

• Lightweight

• Cost of materials

• Protect the head

Multiple Choice

When developing a new bicycle helmet, which of the following is an example of a design criterion?

• The helmet must provide a high level of impact protection.

• The cost of the materials used to make the helmet.

• The amount of time available to develop the helmet.

• The limits of current manufacturing technology.

Multiple Choice

A design team for a new bicycle helmet discovers a new material that offers much higher impact protection, but this material is also very expensive. What does this situation represent?

• A conflict between a key criterion (protection) and a constraint (cost).

• A failure to meet any of the design criteria for the helmet.

• A project that has no clear design constraints.

• A design that perfectly balances all criteria and constraints.

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Common Misconceptions

Misconception	Correction
An object at rest has no forces acting on it.	An object at rest has balanced forces, resulting in a net force of zero.
Action-reaction forces cancel each other out.	They act on different objects, so they do not cancel each other out.
Only large objects exert significant forces.	Even small objects exert an equal and opposite force.
Helmets make you completely safe from concussions.	Helmets reduce injury risk, but they cannot prevent all concussions.

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Summary

Poll

On a scale of 1-4, how confident are you in using Newton's Third Law to explain a collision?

• 1 (Not at all confident)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)