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Forces

Forces. Brigitte Steinmetz John Adams Middle School. Motion. What is motion? An object is in _______ when the distance from another object _________. motion. changes. It moved away from the box!. Distance. What is distance? Distance is the ______________________.

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Forces

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  1. Forces Brigitte Steinmetz John Adams Middle School

  2. Motion • What is motion? • An object is in _______ when the distance from another object _________. motion changes It moved away from the box!

  3. Distance • What is distance? • Distance is the ______________________. • We measure this using the metric system…meters, centimeters, kilometers. • Miles, feet, inches are BAD words in science! length something travels

  4. Speed • What is speed? • _______ = the distance traveled in a certain amount of time. • We can calculate distance using math: • Yes…math is used in science!  Speed Speed = Distance ÷ Time

  5. Velocity • What is velocity? • If you know the _______ and __________ of an object you know the velocity. speed direction Velocity = Speed that has direction

  6. Acceleration • What is acceleration? • When the speed or direction of an object _________ we call it “acceleration”. • Increasing Speed (↑) • Decreasing Speed (↓) • Change Direction changes Acceleration = change in velocity.

  7. Force • What is a force? • Push or pull. • You put force on your pencil when you push it or pull it.

  8. Unbalance vs. Balanced Forces UnbalancedTwo forces can combine and add together making it a stronger one! + = Net Force UnbalancedA bigger force can push against a smaller force and subtract from each other making a weaker one! = + Net Force BalancedTwo equal forces can push against each other and cancel each other out! + = 0 Net Force

  9. Isaac Newton • English Mathematician • Lived during the 1600s • Came up with three laws of motion.

  10. Law of Inertia – 1st Law • An object that is _________________ will stay still. • An object that is moving at a constant (doesn’t change) velocity will keep moving at that same velocity… • Unless an unbalanced force acts on it. still (not moving) Isaac. What are you talking about?

  11. Law of Inertia – 1st Law • The unbalanced force = _________ • The car and the person want to keep moving. The car stops because of the wall, BUT the person keeps moving because there is not a force stopping him. • What kind of unbalanced force should the person be wearing to stop him at the same time the wall stopped the car? http://www.physicsclassroom.com/mmedia/newtlaws/cci.html - May 5th, 2004 wall Seat Belt

  12. Newton’s 2nd Law • Objects with a larger mass take more force to move than objects that have a smaller mass. • Smaller mass objects accelerate faster than bigger mass objects if the same amount of force is used to move it. Force = Mass x Acceleration

  13. Newton’s 2nd Law F = 1000 kg x .05 m/s2 F = 50 m/s2 F = 2000 kg x .05 m/s2 F = 100 m/s2

  14. Law of Gravitation – 3rd Law gravity • All objects attract other objects – called ________. • The amount of gravity (attraction) depends on the mass (# of atoms it is made of) of the object. • The bigger the mass the more attractive it is. • Why don’t you stick to your table like you do to the Earth? • The Earth is HUGE! It attracts you more than the book can. So, you and the book stick to the Earth!

  15. Law of Gravitation – 3rd Law • If in object is pushed it will push back with the same (equal) amount of force. • If an object is pulled it will pull back with the same (equal) amount of force.

  16. Newton’s 2nd & 3rd Laws • Which do you think will hit the ground first? • A. Elephant • B. Feather • C. They will land at the same time. • Explain your answer.

  17. Newton’s 2nd & 3rd Laws • What happened? • Explain why you think this happened. http://www.physicsclassroom.com/mmedia/newtlaws/efff.html - May 5th, 2004.

  18. Newton’s 2nd & 3rd Laws Find the acceleration for both rocks. http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l3e.html - May 5th, 2004

  19. Newton’s 2nd & 3rd Laws • All objects have the same _________when they free falling. http://www.glenbrook.k12.il.us/gbssci/phys/Class/1DKin/U1L5e.html - May 5, 2004 • The bigger mass objects have a bigger overall force pulling them down. • Attraction between the bigger rock and Earth is more than the smaller rock. acceleration

  20. Newton’s 2nd & 3rd Laws • What might cause the feather to land after the elephant? http://www.physicsclassroom.com/mmedia/newtlaws/efff.html - May 5th, 2004.

  21. Newton’s 2nd & 3rd Laws • Air pushing up on both. This kind of force is called ____________. unbalanced http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l3e.html - May 5th, 2004

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