Newton's laws of motion

Newton's laws of motion

His full title is Sir Isaac Newton and he was an English Physicist and Mathematician.

​Investigate 3 discoveries from Newton and how this has influenced other scientists to discover concepts or create new inventions.

​Who is Isaac Newton?

The first law of motion:

The first law of motion is inertia and can be described as:

The tendency for an object to resist change in its state of motion.

In simple terms, an object will keep moving unless an unbalanced force stops it, the opposite can be true for an object not moving.

Inertia

An example of inertia is kicking a soccerball. The ball will not move until it is kicked, and will only stop when a foot (for example) stops it.

So from the video, we have learned...

An object with a smaller mass will have less inertia. The opposite is true for a heavier object.

Mass is the measurement of inertia.

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​Inertia

A baseball player throws the ball. According to inertia, what does the ball want to do?

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​Inertia

Now we've established what the ball will do according to inertia. What unbalanced forces do you think will try and stop it from moving?

​Inertia

• Gravitational forces

• Air resistance

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Inertia

​The second law of motion:

The second law of motion is forces and can be described as:

A force applied to an object will determine the acceleration of the object. This means the greater the force, the greater the acceleration.

Forces

Let's look at the soccerball example again, if you kick the ball softly, it will not move far or go very fast. However, if you kick the ball hard it will accelerate fast and move further.

​Forces

Before we can expand on the second law of motion, we need to understand what forces are.

A force is a push or pull motion on an object resulting from two objects interacting with one another. When the interaction ends, the two objects no longer experience the force.

Forces only exist as a result of an interaction.

Forces

Forces can be separated into two categories: contact or non-contact. From the list below tell me which category you think the force falls into.

Gravitational

Frictional

Tension

Electrical

Air resistance

Spring

Magnetic

Applied

Normal

Forces

What two factors do you think acceleration relys on?

Forces

What two factors does acceleration rely on?

• Directly on the net force

• Inversely on the objects mass

Forces

​Forces

​Example...

The third law of motion:

The third law of motion is known as action and reaction, which can be described as:

Every action has an equal and opposite reaction.

When an object exerts a force on another object, the second object will exert an equal and opposite force back on the first object.

Action and reaction

Another example can be a person sitting in a chair. The person will exert a downward force on the chair and the chair will exert an upward force on the person (action and reaction).

Newton's laws of motion

Now that we have learned all of the laws of motion, let's see if we can name which law applies to different scenarios.

Multiple Choice

A swimmer pushes back on the water and moves forward

• First law (inertia)

• Second law (forces)

• Third law (action and reaction)

Multiple Choice

A picture frame is hanging on a wall and does not move

• First law (inertia)

• Second law (forces)

• Third law (action and reaction)

Multiple Choice

Several dogs pulling a sled cause it to accelerate more quickly than just one dog pulling a sled.

• First law (inertia)

• Second law (forces)

• Third law (action and reaction)

Multiple Choice

You kick a bowling ball and a tennis ball with the same amount of force. The tennis ball travels farther than the bowling ball.

• First law (inertia)

• Second law (forces)

• Third law (action and reaction)

Multiple Choice

A bird flaps its wings down and the air pushes the bird upwards

• First law (inertia)

• Second law (forces)

• Third law (action and reaction)

Multiple Choice

A student leaves a pencil on their desk and the pencil stays in the same spot until another student picks it up.

• First law (inertia)

• Second law (forces)

• Third law (action and reaction)