1 Newton’s Laws The Father of Force Isaac Newton (1642 – 1727)

2 What is a Force? Force can be defined as a push or a pull. Or anything else that has the ability to change motion

3 Force: kg x m/s 2 kilogram x m/sec 2 N Is even easier! Easier than saying kilogram  m/sec 2

4 To Understand Force… You must understand the difference between AND 2 Kg Mass

5 Mass What is Mass? 1 Kg Mass 2 Kg Mass 1.5 Kg Mass The amount of “stuff” in an object. Mass is measured in K KK Kilograms

6 How is Mass Different Than Weight? 1.0 Kg Mass 2.2 pounds 9.8 N 1.5 Kg Mass 3.3 pounds 14.8 N 2.0 Kg Mass 4.4 pounds 19.7 N Weight is measurement of FORCE. kilograms (kg)weight (force) USE pounds (lb) or N for force DON’T USE kilograms (kg) as a measurement for weight (force) USE pounds (lb) or N for force. (1 kg x 9.86 m/s 2 ) (1.5 kg x 9.8 6m/s 2 ) (2 kg x 9.86 m/s 2 ) force due to gravity (9.8 m/s 2 )

7 1 Kg Mass 2.2 Pounds On the sun 1.0 kg would weigh 59.5 lbs On Mars 1.0 kg would weigh 0.8 lbs On the moon 1.0 kg would weigh 0.3 lbs Different Gravity? Mass is the Same:1 kg But the WEIGHT… What’s “Your Weight On Other Worlds?” 7

8 Let’s look at Newton's three laws of motion... These laws explain why objects move (or don't move).

9 An object will remain at rest unless acted upon by an “unbalanced” force. An object in motion will continue with constant speed and direction, unless acted on by an unbalanced force. This law shows how force, mass and acceleration are related as shown in the equation below: Force = mass x acceleration For every action there is an equal and opposite reaction

10 Newton’s First Law: Balanced Forces Forces that are balanced can be: In Motion Not in motion Stay at rest: a book on a table Stay in motion: a bowling ball tossed in space Inertia An object will maintain a constant state of motion (balanced). This means an object at rest tends to stay at rest and an object in motion tends to stay in motion It will go on and on forever This is known as IP&C Table pushes up on book Gravity pulls down on book

11 Newton’s First Law: Unbalanced Forces The book below slides and then stops because resistant force called friction. Friction is force that opposes motion. In space there is no resistance to cause friction, so a bowling ball would stay in motion...unless another object got in the way… It kind of reminds of a few movies I’ve seen lately... An unbalanced force is a force that changes the motion. IP&C Force of friction stops the book

12 Of course “frictional” force happens on earth... But, if you weren’t wearing a safety belt You would continue your motion… Don’t let this happen to you, buckle up!

13 Force and acceleration are related Newton’s Second Law: Force = Mass X Acceleration You are going down the road on your inline skates. Suddenly you look to your right and see a car accelerating faster coming right for YOU! You look for an escape to your left… Oh no! There’s a rock at the edge of neatly manicured lawn. Which will you choose... A massive car accelerating faster?...or a medium size rock not in motion? Good Choice Force (car) = mass x acceleration is greater than Force (rock) = mass x acceleration You still might get hurt, but would be much worse off choosing the force of the car over the force of the rock.

14 Solving Force Problems Step 1 Read the problem and write down the formula you will use. Step 2Plug in the information you know into the formula. Step 4Write down the answer with the correct units. Step 3Solve the math.

15 “How much force is needed to accelerate a 1400-kg car 2 m/s 2 ? ” Consider the problem… F = m = a = FormulaPlug-inAnswer Units, units, units! Step 1Read the problem, draw a picture 1400-kg car 2 m/s 2 How much force?

16 F = m = a = FormulaPlug-inAnswer Units, units, units! 1400 kg 2 m/s 2 Step 2Write down what you know, What are you trying to find? 1400-kg car 2 m/s 2 “How much force is needed to accelerate a 1400-kg car 2 m/s 2 ? ”

17 FormulaPlug-inAnswer Units, units, units! Step 3Set up the formula, F = m = a = 1400 kg 2 m/s 2 m x a “How much force is needed to accelerate a 1400-kg car 2 m/s 2 ? ” F = m x a

18 FormulaPlug-inAnswer Units, units, units! Step 4Plug in the numbers Solve 2800kg x m/s 2 F = m = a = 1400 kg 2 m/s 2 “How much force is needed to accelerate a 1400-kg car 2 m/s 2 ? ” m x a 1400 kg x 2 m/s kg x m/s 2

19 Be sure to do the problems: Helpful Hints: a = F / m F = m x a m = F / a

20 The unit for force: 1 kg x m/s 2 = 1 newton or 1N …I thought so. Which one would you rather write for your answer? 2800 N

21 Newton’s Third Law: Action / Reaction For every action there is an equal and opposite reaction Look at the picture below: What is the action? What is the reaction? As the gases push downward out of the rocket, The the rocket is pushed upward by the gases

22 An object will remain at rest unless acted upon by an “unbalanced” force. An object in motion will continue with constant speed and direction, unless acted on by an unbalanced force. This law shows how force, mass and acceleration are related as shown in the equation below: Force = mass x acceleration For every action there is an equal and opposite reaction

23 Newton’s Laws explain how Earthquakes create such devastation Most of the time the Earth’s massive plates push on each to move very slowly. mass force But, sometimes a massive plate exerts a greater amount of force that accelerate another plate. To learn more go to: This results in an earthquake.

24 The Story of Newton’s Apple Newton sat under an apple tree and an apple fell on his head. That falling apple gave him a revelation. GRAVITY. But DON’T think of gravity as falling… It is the pull (force) that an object has on another. And led him to describe a force called...

25 Newton’s apple was falling because the massive gravitational force of the Earth was pulling the apple towards Earth...

26 Gravity is the force that ALL objects in the UNIVERSE exert on each other... 2 things Newton said that gravitational force depends on 2 things: DISTANCE The DISTANCE of the objects MASS The MASS of the objects LESS gravitational force compared to... MORE gravitation force here. blue object green object blue object MASS The blue object has more gravitational force than the green object because the blue object has more MASS.

27 Newton’s apple fell because the Earth’s pull of gravity.... was more massive than the apple’s pull of gravity on the Earth The itty-bitty pull of apple is too small to pull the Earth, so it is pulled to the Earth...

28 The moon is a satellite too.. The pull of gravity keeps satellites orbiting around the Earth

29 The Earth is round and the satellite continues to “just miss” entering into the Earth’s atmosphere. Satellites are sent away and placed in the exact spot where the Earth’s gravity pulls them into a “continuous free fall” or orbit... The moon does the same thing.

30 Does the moon’s gravitational pull effect the Earth? Yes, the moon’s gravity is large enough to actually pull water out of the ocean from space… Well, not quite that much...just enough to create motion of the tides.

31 Newton is even credited with inventing CALCULUS. Needless to say, Newton was very important in shaping our understanding of science