An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

• In other words, an object will keep doing whatever it’s doing (sitting still or moving) unless an unbalanced force acts on it.

• Example: Your skateboard will stay lying in the driveway until someone moves it. And, if your skateboard suddenly hits a curb and stops short, you will keep moving until something stops you!

• Newton’s 1st Law of Motion is also known as the Law of Inertia.Inertia.

• Inertia is an objectInertia is an object’’s tendency to resist a s tendency to resist a change in motion.change in motion.

• The greater an objectThe greater an object’’s mass, the greater s mass, the greater its inertia, and the larger the force needed its inertia, and the larger the force needed to overcome the inertia.to overcome the inertia.

•Which vehicle would take longer to stop?

Examples of Newton’s 1st Law: The Law of Inertia

Think about what you have learned about Newton’s 1st Law, the Law of Inertia.

With a partner, think of an example to share.

Newton’s 1st Law and You

Because of inertia, objects (including you) Because of inertia, objects (including you) resist changes in motion. resist changes in motion.

When the car going 80 km/hour is stopped When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at by the brick wall, your body keeps moving at 80 km/hour.80 km/hour.

Newton’s 2nd Law

Force= mass x acceleration

The greater the force applied to an object, the more the object will accelerate.

It takes more force to accelerate an object with a lot of mass than to accelerate something with very little mass.

–The greater the force, the greater the acceleration.–The greater the mass, the greater the

force needed for the same acceleration–Calculated by: F = ma– (F = force, m = mass, a =

acceleration)

Examples of Newton’s 2nd Law

Think about what you have learned about Newton’s 2nd Law.

With a partner, think of an example to share.

Newton’s 3rd Law

• For every action force, there is an equal and opposite reaction force. (Forces are always found in pairs.)

• Athlete pushes bar upwards.• Bar pushes the athlete downwards.

• Bowling ball pushes pin to the right.• Pin pushes bowling ball to the left.

Newton’s 3rd Law

Newton’s 3rd Law

Inside rocket, fuels are Inside rocket, fuels are burned in the engine, burned in the engine, producing hot gases. producing hot gases.

The hot gases push against The hot gases push against the inside tube of the rocket the inside tube of the rocket and escape out the bottom and escape out the bottom of the tube. As the gases of the tube. As the gases move downward, the rocket move downward, the rocket moves in the opposite moves in the opposite direction.direction.

Examples 3rd Law

Think about what you have learned about Newton’s 3rd Law.

With a partner, think of an example to share.