Newton's 1st Law

Newton's 1st Law

Inertia

• We will define inertia and describe it as Newton’s first law of motion.

  I will identify a scenario as Newton’s First Law (law of inertia) and explain why it is that law.

Sir Isaac Newton

Sir Isaac Newton (1643-1727) an English scientist and mathematician famous for his discovery of the law of gravity also discovered the three laws of motion.  Today these laws are known as Newton’s Laws of Motion and describe the motion of all objects on the scale we experience in our everyday lives.

Because of Inertia, if it is still it will not move unless…..*

INERTIA!

The tendency of objects to resist a change in motion.

If it is moving – it will keep moving. If it is still – it will not move.

UNLESS….. An unbalanced force acts on it!

Why do moving object continue to keep on moving?

INERTIA!

The tendency of objects to resist 
a change in motion.

If it is moving – it will keep moving. If it is still – it will not move.

UNLESS….. an unbalance force acts on it!

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Multiple Choice

According to Newton’s first law of motion, an object at rest that is not acted on by an unbalanced force will

• remain in motion.
• eventually come to a stop.
• change its momentum.
• remain at rest

Multiple Choice

According to Newton’s first law of motion, a moving object that is not acted on by an unbalanced force will

• remain in motion.
• eventually come to a stop.
• change its momentum.
• accelerate.

Multiple Choice

What is inertia?

• the force that opposes motion
• the force of attraction between 2 objects
• an object's tendency to stay in motion or to stay at rest
• a change in an object's speed and/or direction

Mass and Inertia

-  All objects have inertia

- Inertia is based on MASS

-More Mass-More Inertia

-Less Mass-Less Inertia

Multiple Choice

Which has more inertia?

Multiple Choice

Which has more inertia?

Multiple Choice

Which has more inertia?

Multiple Choice

Why does an 18-wheeler have more inertia than a bicycle?

• it has more mass
• it has more volume
• it is not as aerodynamic

How are balanced forces related to inertia?

If an object is at rest, all of the forces on it are balanced. 

If an object is moving at a constant velocity all of the forces are balanced.

Multiple Choice

The tendency of an object at rest to stay at rest unless it is acted upon by a force is called ___________________

• inertia
• motion
• gravity
• lubricant

Multiple Choice

Which could be an example of a balanced force?

• An asteroid moving at a constant speed through space 
• A car accelerating from a stop sign
• A box of dishes falling from a counter 
• A rocket taking off 

Multiple Choice

A wheeled cart is moving to the right at a constant speed.  Two forces of equal magnitude are acting upon the cart. Which of the following best describes the forces and motion of the cart?

• Balanced Forces, Constant Speed
• Balanced Forces, Acceleration
• Unbalanced Forces, Constant Speed
• Unbalanced Forces, Acceleration

Open Ended

How are unbalanced forces related to inertia?

What do you think will happen next ?What will happen to the coin when the cardboard is pulled quickly?

The coin has inertia, meaning it really wants to stay in one place. 

The coin has inertia, meaning it really wants to stay in one place.  The coin does not move with the card the coin, falls due to the unbalanced force of gravity.

Multiple Choice

This illustration explains inertia because the object stays at rest until an unbalanced force is applied. What is the unbalanced forced that changed the coin?

• coffee

• motion

• inertia

• gravity

Open Ended

When the car stops, what happens to the driver? Why it is important to wear a seat belt ?How does this relate to Newton’s first law/ Inertia??

Inertia is the reason that people in cars need to wear seat belts

•  A moving car has inertia, and so do the riders inside it.

• When the driver applies the brakes, an unbalanced force is applied to the car

• The seatbelt applies an unbalanced force to the driver.

Multiple Choice

Which of the following is the best example of Newton's First Law of Motion?

• Jessica's body flies forward after she hits the brakes

• Jessica drives a car

• Jessica is at a road crossing

• Jessica is sleeping

Multiple Choice

A person is pedaling their bike and suddenly hits the front brakes and their body continues to move and they fly over the handlebars. The body was an object in motion. When the bicycle stops the body resists changing motion and keeps moving. Gravity overcomes the inertia and the person falls to the ground.

Which part of the scenario describes the Inertia ?

• When the bicycle stops the body resists changing motion and keeps moving

• Gravity overcomes the inertia and the person falls to the ground.

Multiple Choice

A person is pedaling their bike and suddenly hits the front brakes and their body continues to move and they fly over the handlebars. The body was an object in motion. When the bicycle stops the body resists changing motion and keeps moving. Gravity overcomes the inertia and the person falls to the ground.

Which part of the scenario describes the unbalanced force acted upon the object?

• When the bicycle stops the body resists changing motion and keeps moving

• Gravity overcomes the inertia and the person falls to the ground.

Multiple Choice

The inertia in the puck keeps it at rest until the inertia is overcome by the force of the stick hitting it. Which part of the scenario describes the Inertia?

• The inertia in the puck keeps it at rest

• inertia is overcome by the force of the stick hitting it.

Multiple Choice

The inertia in the puck keeps it at rest until the inertia is overcome by the force of the stick hitting it. Which part of the scenario describes the unbalanced force acted upon the object?

• The inertia in the puck keeps it at rest

• inertia is overcome by the force of the stick hitting it.