Newton

Newtons Laws of Motion

The first Law

Background

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.

He published them in his book Philosophiae Naturalis Principia Mathematica (mathematic principles of natural philosophy) in 1687. 

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.

Newton’s Laws of Motion

1. An object in motion tends to stay in motion and an object at rest tends to  stay at rest unless acted upon by an unbalanced force.

2. Force equals mass times acceleration

 (F = ma).

3. For every action there is an equal    and opposite reaction.

Newton’s First Law

1. An object at rest tends to stay at rest and

Newton’s First Law

1. An object in motion tends to stay in motion unless acted upon by an unbalanced force.

Open Ended

What does Newton's First Law mean?

What does this mean?

Basically, an object will “keep doing what it was doing” unless acted on by an unbalanced force. If the object was sitting still, it will remain stationary. If it was moving at a constant velocity, it will keep moving. It takes force to change the motion of an object.

What is meant by Force

• A force is a push or a

pull acting upon an object as a result of its

interaction with another object.

• Force has the

symbol F and is measured in newtons (N).

• In relation to motion, a force is something that can change an object’s motion.

What is meant by unbalanced force?

• If the forces on an object are equal and opposite,
• They are said to be balanced, and the object experiences no change in motion. Rests.

What is meant by unbalanced force?

• If they are not equal and opposite,
• Then the forces are unbalanced and the motion of the object changes.
• Moves or changes direction

Equal and Opposite directions Balanced

Net force = 0N

Poll

A soccer ball is sitting at rest. What does is need to change its motion?

• It needs a balanced force of a kick.

• It needs gravity

• It needs an unbalanced force of a kick

• Needs equal and opposite directions balanced.

Some Examples from Real Life

• A soccer ball is sitting at rest. 
• It takes an unbalanced force of a kick to change its motion.

Some Examples from Real Life

• Two teams are playing tug of war. 
• They are both exerting equal force on the rope in opposite directions. 
• This balanced force results in no change of motion – zero Net Force.

Newton’s First Law is also called the Law of Inertia

• Inertia: the tendency of an object to resist changes in its state of motion
• The First Law states that
• all objects have inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).

Open Ended

Can you provide examples of objects that may have differences in is inertia?

Mass and Inertia

Objects with more mass have more inertia than an object with a smaller mass

Mass

• The mass of an object affects its' inertia.
• Objects with more mass have more inertia than an object with a smaller mass.
• It's harder to make a large object move or change speed and direction when it's moving.

Moving Objects

• Things don’t keep moving forever because there’s almost always an unbalanced force acting upon it.
• A book sliding across a table slows down and stops because of the force of friction.

Objects and Gravity

If objects in motion tend to stay in motion, why don’t moving objects keep moving forever?

If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

Motion in Outer Space

In outer space, away from Forces of gravity and any sources of friction, a rocket ship launched with a certain speed and direction would keep going in that same direction and at that same speed forever.

Stile App

• Open class stile app.

• Click on Newton's Law of Motion-1.2 The first law of motion

• If your code is expired enter class code S4CHXC

• Complete 20 minutes, head back to meet for quiz.

Multiple Choice

What can a force do?

• start a motion
• stop a motion
• all of the above
• change the direction of the motion

Multiple Choice

friction is a force that acts...

• in the same direction as the motion
• opposite to the direction of the motion
• opposite to the applied forces
• the same direction as the applied force

Multiple Choice

What is the name for a push or pull?

• A movement
• A force
• Speed
• Density

Multiple Choice

An object need a balanced force for the object to move. 

• True
• False

Multiple Choice

If an object is not moving the forces acting upon it are _____________

• unbalanced
• weak
• balanced
• Hulk Smash!

Multiple Choice

Which type of force(s) will cause a change in an object's motion?

• gravity
• zero net force
• balanced forces
• unbalanced forces

Multiple Choice

Which has more Inertia? (so need more force to move) 

• Truck
• Ant
• A cat
• A skateboard

Multiple Choice

What kind(s) of objects have inertia?

• all objects with mass
• only objects at rest
• only objects in motion
• only objects whose motion is being changed

Multiple Choice

What is the net force?

• 20 N 
• 0 N 
• 400 N 
• 40 N 

Multiple Choice

__________ is the sum of all forces acting on an object. It is capable of accelerating a mass. 

• velocity
• gravity
• net force
• distance

Multiple Choice

Balanced or unbalanced?

• balanced
• unbalanced

Multiple Choice

The tendency of an object to resist a change in its motion

• acceleration
• inertia
• mass
• frame of reference

Multiple Choice

If one object has twice as much mass as another object, it also has twice as much...

• inertia
• velocity
• acceleration due to gravity
• DO NOT PUSH ME

Multiple Choice

What is Newton's First Law known as? The Law of

• Friction
• Mass
• Inertia
• Gravity

Multiple Choice

What is Newton's First Law

• F=ma
• Every action has an equal and opposite reaction
• An object at rest stays at rest, an object in motion stays in motion. 
• Friction 

Multiple Choice

What is Newton's First Law known as? The Law of

• Friction
• Mass
• Inertia
• Gravity