1. Brain Teaser
What causes the wheels on the car to continue to keep moving?
How long will the wheels continue to move after a car is parked?

2. Newton’s 1st Law of Motion
Physical Science

3. Background
Sir Isaac Newton is famous for his discovery of the law of gravity and he also discovered the three laws of motion.
There are three laws of motion, today we will discuss the first.

4. Newton’s Three Laws
All of Newton’s Laws are about forces and motion A force is a push or pull that one object exerts on another object The net force is the total amount of forces in the system

5. Newton’s First Law
Newton’s First Law says that an object in motion will remain in motion, and an object at rest will remain at rest, unless an external force acts upon it

6. 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. all objects have inertia The more mass an object has, the more inertia it has (and the harder it is to change its motion).

7. Inertia is determined by MASS
For example: a Semi-truck has more inertia than a soccer ball because it has a larger mass and therefore a larger tendency to stay at rest or in motion

8. Newton’s First Law
Objects eventually stop moving because of friction which is a force

9. 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 still. If it was moving at a constant velocity, it will keep moving. It takes a force to change the motion of an object.

11. Some Examples from Real Life
A soccer ball is sitting at rest. It takes an unbalanced force of a kick to change its motion.
On your way to school, a bug flies into your windshield. Since the bug is so small, it has very little inertia and exerts a very small force on your car (so small that you don’t even feel it).

12. If objects in motion tend to stay in motion, why don’t moving objects keep moving forever?
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.
If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

13. Newtons’s 1st Law and You
Because of inertia, objects (including you) resist changes in their motion. When the car going 70 mph is stopped by the brick wall, your body keeps moving at 70 mph.

14. Writing Assignment: Newton’s 1st Law Journal Prompt
Write a letter to your brother or sister explaining how seat belts help to save lives. Please explain why it is so important for younger kids to sit in the backseat.
Include the terms: injury, seat belts, velocity, Newton’s first law, inertia, balanced force, unbalanced force.