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Students will understand and apply Newton's First Law of Motion to real-world scenarios.

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By the end of the lesson, students will be able to:
- Explain Newton's First Law of Motion
- Identify examples of objects at rest or in motion
- Analyze real-world applications of the law

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Essential Question: Why does a passenger move forward when a bus suddenly stops?<br>Students discuss in pairs and share their thoughts using Padlet's collaboration wall.

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Students perform the 'Coin and Card Trick':
1. Place a card on a glass with a coin on top
2. Quickly flick the card horizontally
3. Observe and explain what happens to the coin

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For Science! The coin inertia experiment

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In groups of 4, students investigate inertia using everyday objects (books, balls, etc.). They record observations and explanations on a shared Padlet board.

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Students explore forces and motion using PhET simulation

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Explore the forces at work when pulling against a cart, and pushing a refrigerator, crate, or person. Create an applied force and see how it makes objects move. Change friction and see how it affects the motion of objects.

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Students design a safety device for vehicles based on Newton's First Law. Quick sketches and explanations.

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For advanced students: Research and explain how Newton's First Law applies in space exploration.

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Throughout the lesson:
- Monitor group discussions
- Check concept understanding during demonstrations
- Review student explanations on Padlet boards

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Students complete a 3-question digital quiz:
1. Define inertia
2. Explain Newton's First Law
3. Provide a real-world example

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Students write:
3 things they learned
2 things they found interesting
1 question they still have

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Share key takeaways and address common misconceptions identified during the lesson

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Students photograph or video 3 examples of Newton's First Law in their daily lives and explain each on their individual Padlet page

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Complete interactive problems on Newton's Laws

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In a previous chapter of study, the variety of ways by which motion can be described (words, graphs, diagrams, numbers, etc.) was discussed. In this unit (Newton's Laws of Motion), the ways in which motion can be explained will be discussed. Isaac Newton (a 17th century scientist) put forth a variety of laws that explain why objects move (or don't move) as they do. These three laws have become known as Newton's three laws of motion. The focus of Lesson 1 is Newton's first law of motion - sometimes referred to as the law of inertia.

Newton's first law of motion is often stated as

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.

Two Clauses and a Condition

There are two clauses or parts to this statement - one that predicts the behavior of stationary objects and the other that predicts the behavior of moving objects. The two parts are summarized in the following diagram.

The behavior of all objects can be described by saying that objects tend to "keep on doing what they're doing" ( unless acted upon by an unbalanced force). If at rest, they will continue in this same state of rest. If in motion with an eastward velocity of 5 m/s, they will continue in this same state of motion (5 m/s, East). If in motion with a leftward velocity of 2 m/s, they will continue in this same state of motion (2 m/s, left). The state of motion of an object is maintained as long as the object is not acted upon by an unbalanced force. All objects resist changes in their state of motion - they tend to "keep on doing what they're doing."

There is an important condition that must be met in order for the first law to be applicable to any given motion. The condition is described by the phrase "... unless acted upon by an unbalanced force." As the long as the forces are not unbalanced - that is, as long as the forces are balanced - the first law of motion applies. This concept of a balanced versus and unbalanced force will be discussed in more detail later in Lesson 1.

Suppose that you filled a baking dish to the rim with water and walked around an oval track making an attempt to complete a lap in the least amount of time. The water would have a tendency to spill from the container during specific locations on the track. In general the water spilled when:

the container was at rest and you attempted to move it

the container was in motion and you attempted to stop it

the container was moving in one direction and you attempted to change its direction.

The water spills whenever the state of motion of the container is changed. The water resisted this change in its own state of motion. The water tended to "keep on doing what it was doing." The container was moved from rest to a high speed at the starting line; the water remained at rest and spilled onto the table. The container was stopped near the finish line; the water kept moving and spilled over container's leading edge. The container was forced to move in a different direction to make it around a curve; the water kept moving in the same direction and spilled over its edge. The behavior of the water during the lap around the track can be explained by Newton's first law of motion.

Everyday Applications of Newton's First Law

There are many applications of Newton's first law of motion. Consider some of your experiences in an automobile. Have you ever observed the behavior of coffee in a coffee cup filled to the rim while starting a car from rest or while bringing a car to rest from a state of motion? Coffee "keeps on doing what it is doing." When you accelerate a car from rest, the road provides an unbalanced force on the spinning wheels to push the car forward; yet the coffee (that was at rest) wants to stay at rest. While the car accelerates forward, the coffee remains in the same position; subsequently, the car accelerates out from under the coffee and the coffee spills in your lap. On the other hand, when braking from a state of motion the coffee continues forward with the same speed and in the same direction, ultimately hitting the windshield or the dash. Coffee in motion stays in motion.

Have you ever experienced inertia (resisting changes in your state of motion) in an automobile while it is braking to a stop? The force of the road on the locked wheels provides the unbalanced force to change the car's state of motion, yet there is no unbalanced force to change your own state of motion. Thus, you continue in motion, sliding along the seat in forward motion. A person in motion stays in motion with the same speed and in the same direction ... unless acted upon by the unbalanced force of a seat belt. Yes! Seat belts are used to provide safety for passengers whose motion is governed by Newton's laws. The seat belt provides the unbalanced force that brings you from a state of motion to a state of rest. Perhaps you could speculate what would occur when no seat belt is used.

There are many more applications of Newton's first law of motion. Several applications are listed below. Perhaps you could think about the law of inertia and provide explanations for each application.

Blood rushes from your head to your feet while quickly stopping when riding on a descending elevator.

The head of a hammer can be tightened onto the wooden handle by banging the bottom of the handle against a hard surface.

A brick is painlessly broken over the hand of a physics teacher by slamming it with a hammer. (CAUTION: do not attempt this at home!)

To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrusted downward at high speeds and then abruptly halted.

Headrests are placed in cars to prevent whiplash injuries during rear-end collisions.

While riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb or rock or other object that abruptly halts the motion of the skateboard.

Try This At Home

Acquire a metal coat hanger for which you have permission to destroy. Pull the coat hanger apart. Using duct tape, attach two tennis balls to opposite ends of the coat hanger as shown in the diagram at the right. Bend the hanger so that there is a flat part that balances on the head of a person. The ends of the hanger with the tennis balls should hang low (below the balancing point). Place the hanger on your head and balance it. Then quickly spin in a circle. What do the tennis balls do?

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how are balanced forces related to motion

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Newton's First Law, sometimes referred to as the law of inertia, describes the influence of a balance of forces upon the subsequent movement of an object.