Newton’s Laws of Motion

Sir Isaac Newton was one of the greatest scientists and mathematicians that ever lived. He was born in England on December 25, 1643. He was born the same year that Galileo died. Newton attended Trinity College Cambridge where he became interested in math, physics, and astronomy. Newton had new ideas about motion, which he called his three laws of motion.

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This law is often called "the law of inertia". Inertia: the tendency of all objects to resist any change in motion.

Let’s break it down An object at rest will remain at rest unless acted on by an unbalanced force. What does at rest mean?

Why do objects set in motion stop? Let’s break it down An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Why do objects set in motion stop?

What does this mean? This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.

Let's study the "skater" to understand this a little better. What is the motion in this picture? What is the unbalanced force in this picture? What happened to the skater in this picture? Is there evidence of inertia?

This law is the same reason why you should always wear your seatbelt. What is the motion in this picture? What is the unbalanced force in this picture? What happened to the driver in this picture? Is there evidence of inertia?

Inertia and Mass Objects will smaller mass have less inertia (or the tendency to resist change) than objects with more mass. Inertia makes it harder to push a bus than a bike and easier to stop a bike than a bus moving at the same speed.

More Examples of Newton’s First Law…

Four-Square Inertia Definition Picture An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Inertia Example Other Information Inertia is the tendency of objects to resist a change in motion.

The acceleration of an object depends on the mass of the object and the amount of force applied.

Acceleration of an object depends on the mass of the object. Let’s break it down Acceleration of an object depends on the mass of the object. If the force applied is the same, the acceleration of the empty cart is greater than the acceleration of the full cart.

Acceleration of an object depends on the amount of force applied. Let’s break it down Acceleration of an object depends on the amount of force applied.

What does this mean? Everyone unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance as lighter objects.

Let's study the animations to understand this a little better.

or FORCE = MASS times ACCELERATION The Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation:                                                                  or FORCE = MASS times ACCELERATION

This is an example of how Newton's Second Law works:                                                                                                                                      Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you can compute how much force Mike is applying to the car. Remember Answer: 50 Newtons

Let’s try another one… F= 1,000 x .1 Our formula would be: .1 m/s/s 1,000 Kg Our formula would be: F= 1,000 x .1 Answer: 100 Newtons

Quiz Time If the same amount of force is applied, which vehicle will accelerate faster? Why? Suzie If Suzie uses 50 Newtons of force to begin biking and Billy uses 35 Newtons of force to begin biking who will accelerate faster? Billy

Four-Square Definition Picture The acceleration of an object depends on the mass of the object and the amount of force applied. Second Law Example Other Information The Second Law can be expressed as a mathematical equation: Force = mass x acceleration or F = M x A

For every action there is an equal and opposite re-action.

What does this mean? This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.

Let's study how a rocket works to understand Newton's Third Law. The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.

UP, UP, and AWAY!

The shuttle’s thrusters push the exhaust gases downward as the gases push the shuttle upward with an equal force. More examples… The rabbit’s legs exert a force on Earth. Earth exerts an equal force on the rabbit’s legs, causing the rabbit to accelerate upward. The bat exerts a force on the ball, sending the ball into the outfield. The ball exerts an equal force on the bat, but the bat does not fly toward the catcher because the batter is exerting another force on the bat.

Four-Square For every action there is an equal and opposite re-action. Definition Picture For every action there is an equal and opposite re-action. Third Law Example Other Information The rabbit’s legs exert a force on Earth. Earth exerts an equal force on the rabbit’s legs, causing the rabbit to accelerate upward. Whenever an object pushes another object it gets pushed back in the opposite direction equally hard.

1. Who was the scientist who gave us the Laws of Motion. 2 1. Who was the scientist who gave us the Laws of Motion? 2. How many Laws of Motion are there? 3. What is another name for the first law of motion? 4. Which law explains why we need to wear seatbelts? 5. Which law says that force is equal to mass times acceleration (F=MA)? 6. Which law says that heavier objects require more force than lighter objects to move or accelerate them? 7. Which law explains how rockets are launched into space? 8. Which law says that for every action there is an equal and opposite reaction?

1. Who was the scientist who gave us the Laws of Motion? Answer: Sir Isaac Newton 2. How many Laws of Motion are there? Answer: three 3. What is another name for the first law of motion? Answer: Law of Inertia 4. Which law explains why we need to wear seat belts? Answer: First Law of Motion 5. Which law says that force is equal to mass times acceleration (F=MA)? Answer: Second Law of Motion 6. Which law says that heavier objects require more force than lighter objects to move or accelerate them? Answer: Second Law of Motion 7. Which law explains how rockets are launched into space? Answer: Third Law of Motion 8. Which law says that for every action there is an equal and opposite reaction? Answer: Third Law of Motion

Works Cited Much of the information, graphics, and animation were gathered from the following website: http://teachertech.rice.edu/Participants/louviere/Newton/