Newton's Laws

I. Newton's First Law DEFINITION An object at rest will remain at rest and an object in motion will remain in motion until acted on by an outside force!

I. Newton's First Law Examples EXAMPLE If your book is sitting at rest on your desk it will remain at rest until an outside force (like a push from you) acts on it If you are riding your bike you will remain in motion until acted on by an outside force (like friction). EXAMPLE

I. Newton's First Law Examples EXAMPLE B lood rushes from your head to your feet while quickly stopping when riding on a descending elevator.

I. Newton's First Law Examples EXAMPLE The head of a hammer can be tightened onto the wooden handle by banging the bottom of the handle against a hard surface.

I. Newton's First Law Examples EXAMPLE To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and, thrusted downward at high speeds and then abruptly halted.

I. Newton's First Law Examples Video Clips Newton's First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica.

Your Turn... You have TWO minutes to write three of your own examples of Newton's First Law of motion in your Science Notebook

Let's review... The law of inertia states that an object _____________. A.) will continue moving in a straight line unless an outside force acts on it. B.) that is NOT moving will not move unless a force acts on it C.) will continue moving at the same velocity unless an outside force acts on it D.) all of the above

Let's review... Th e law of inertia applies to __________. A.) both moving and nonmoving objects B.) moving objects C.) objects at rest

Let's review... Swing a weight on a string around your head in a circular motion. If the string breaks, the weight will most likely… A.) continue to follow a circular path B.) follow a straight-line path

Let's review... A card can be "flicked" from under a penny and fly across the room, but the coin wants to remain in its place (momentarily), the coin is said to have ___________.

II. Newton's Second Law DEFINITION The net force on an object is equal to the power of its acceleration and its mass Force = Mass x Acceleration

So... Newton's Second Law of Motion and it only takes a small force to accelerate an object with a smaller mass. It takes a great force to accelerate an object with a large mass, accelerate- change speed or direction The force required to accelerate an object with a large mass is greater than the force required to accelerate an object with a smaller mass! Large Force Small Force

II. Newton's Second Law FORMULA A force is a push or a pull. To calculate force, we use the following formula: F = ma where F = force in newtons where m = mass in kg where a = acceleration in m/sec 2

How do rubber bullets work?

II. Newton's Second Law Practice Problem #1 With what force will a car hit a tree if the car has a mass of 3,000 kg & it is accelerating at a rate of 2 m/s 2 ? Pull F = (3,000 kg) (2 m/s 2 ) F = 6,000 kg m/s 2 F = 6,000 N ANSWER

A 10 kg bowling ball would require what force to accelerate it down an alleyway at a rate of 3 m/s 2 ? Pull ANSWER: F = (10 kg) (3 m/s 2 ) F = 30 kg m/s 2 F = 30 N Problem #2 using formula F = ma

Problem # 3 using formula a = F/m What is the acceleration of a softball if it has a mass of 0.50 kg & hits the catcher's glove with a force of 25 newtons? Pull a = Fa = 25 N m 0.50 kg a = 50 m/s 2 ANSWER

Problem # 4 using formula F = ma What is the mass of a truck if it is accelerating at a rate of 5 m/s 2 & hits a parked car with a force of 14,000 newtons? Pull m = Fm = 14,000 N a 5 m/s 2 m = 2,800 kg ANSWER

III. Newton's Third Law DEFINITION Common expression of 3 rd Law is, To every action there’s an equal and opposite reaction

So... Newton's Third Law of Motion If a hammer exerts a force on a nail (action) then the nail exerts an equal and opposite force back on the hammer (reaction), causing the hammer to suddenly stop. When a rocket launches as the fuel burns it emits exhaust out the bottom of the rocket (action) and then the rocket is pushed in the up in the opposite direction (reaction). For every action there is an equal and opposite reaction!

III. Newton's Third Law Demo Desk and Rolling Chair Flash

ACTION Reaction

III. Newton's Third Law Newton's Laws

II. Newton's Third Law

In the boxes above you will read several examples of motion. Decide which of Newton's three Laws of Motion is described in each box. Click on the box and the answer will be revealed.