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1 st Law 3 rd Law 2 nd Law People DO NOT create laws governing the natural world. We only identify identify the principles that exist in the physical.

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Presentation on theme: "1 st Law 3 rd Law 2 nd Law People DO NOT create laws governing the natural world. We only identify identify the principles that exist in the physical."— Presentation transcript:

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2 1 st Law 3 rd Law 2 nd Law

3 People DO NOT create laws governing the natural world. We only identify identify the principles that exist in the physical world and name them for reference!!

4 What makes objects move? What makes objects move? What makes them change their motion? What makes them change their motion?

5 Force Contact Force – when 2 objects must be touching to exert forces on each other Contact Force – when 2 objects must be touching to exert forces on each other Friction Pushing or kicking a ball Long-Range Force – a force that is exerted without the objects having to touch Long-Range Force – a force that is exerted without the objects having to touch Gravity Magnetism Nuclear force Force – a push or a pull Force – a push or a pull

6 Net force – combination of all forces acting on an object Net force – combination of all forces acting on an object COMBINING FORCES Balanced Forces – 2 or more forces acting on an object cancel each other – they do NOT change the motion of the object (Net Force = 0) Balanced Forces – 2 or more forces acting on an object cancel each other – they do NOT change the motion of the object (Net Force = 0) Unbalanced Forces –forces acting on an object do NOT cancel each other – they DO change the motion of the object (Net Force 0) Unbalanced Forces –forces acting on an object do NOT cancel each other – they DO change the motion of the object (Net Force 0)

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9 REST The state of an object when it is not changing position. THIS IS RELATIVE!! Not moving in relation to your immediate surroundings!!!

10 MOTION The state of an object when it is changing position in relation to its surroundings. THIS IS RELATIVE, TOO!! When you are sitting on an airplane, you are at rest, but if you get up and walk down the aisle, you are in motion.

11 If you are sitting in a seat on a speeding airplane you would still be considered at rest! If rest were defined as a total absence of motion, it would not exist in nature.

12 UNBALANCED FORCES If an object is at REST, it takes an unbalanced force to make it move. If an object is in MOTION, MOTION, it takes an unbalanced force to stop it, it, change its direction direction from a straight line path, or alter its speed.

13 ACCELERATION

14 Balanced Forces There is no change in motion therefore no acceleration Unbalanced Forces There is a force pushing the book to the RIGHT that is GREATER than the force of FRICTION therefore there is acceleration.

15 Newtons 1 st Law of Motion Lazy, resistant to change!!!

16 Newtons 1 st Law of Motion If there is NO net force acting on an object then If there is NO net force acting on an object then An object at rest will remain at rest An object in motion will remain in motion at constant speed. Until acted upon by an outside force The truck stops when it hits the car, the ladder continues moving forward because the force of the car was acting on the truck NOT the ladder.

17 Newtons 1 st Law of Motion From a standing start the truck moves away very quickly causing the passenger to fall backward After traveling at some speed the truck suddenly comes to a stop causing the passenger to fall forward. Force was applied to the truck not the passenger!!!

18 Newtons 1st Law of Motion MASS OF AN OBJECT = INERTIA OF AN OBJECT More mass = more inertia (greater resistance to change (greater resistance to change) Less mass = less inertia (smaller resistance to change)

19 Newtons 1st Law of Motion MASS OF AN OBJECT = INERTIA OF AN OBJECT INERTIA of an object explains why a magician can pull the tablecloth out from under a set of glasses without having them fall over The glasses have more inertia than the tablecloth as the force (pull) is applied to the tablecloth.

20 Newtons 2 nd Law of Motion Force is equal to mass times acceleration

21 Newtons 2 nd Law of Motion Cannon

22 When the cannon is fired, an explosion propels a cannon ball out the open end of the barrel. It flies to its target. At the same time, the cannon itself is pushed backward a meter or two. ACTION - work What happens to the cannon and the ball is determined by Newtons 2 nd Law. Newtons 2nd Law of Motion

23 F = m (cannon) a (cannon) F = m (ball) a (ball) Force (exploding gunpowder) is the same for the two equations, they can be combined and re-written m (cannon) a (cannon) = m (ball) a (ball)

24 Acceleration and Mass Force – Spring-loaded plunger m (cart1) a (cart1) = m (cart2) a (cart2)

25 NEWTON The standard unit of force 1 newton = the force required to accelerate a mass of 1 kilogram at 1 meter per second per second

26 1 Newton of Force = 1 kg mass x 1 m/s 2 acceleration

27 Newtons Third Law of Motion For every action there is an equal and opposite reaction For every action there is an equal and opposite reaction

28 Balloons & Rockets?

29 Balloons & Rockets Air inside a balloon is compressed by the balloons rubber walls. Air inside a balloon is compressed by the balloons rubber walls. The air pushes back so that the inward and outward pressing forces balance. The air pushes back so that the inward and outward pressing forces balance. When the nozzle is released, air escapes through it and the balloon is propelled in the opposite direction. When the nozzle is released, air escapes through it and the balloon is propelled in the opposite direction.

30 Rocket Flight Forces become balanced and unbalanced all the time.

31 Launch pad Launch padBalanced surface of pad pushes the rocket up gravity tries to pull it down Apollo 11

32 Engines Ignited Engines IgnitedUnbalanced Thrust from rocket pushes up gravity tries to pull it down Rocket travels upward Apollo 11

33 Rocket in travel – rocket runs out fuel Rocket in travel – rocket runs out fuelUnbalanced Rocket will slow down Stops at its highest point Gravity pulls it back to Earth Apollo 17 Apollo 11

34 Orbiting Satellite

35 Controlling velocity is extremely important for maintaining the circular orbit of the spacecraft Only an unbalanced force such as friction with gas molecules in orbit or the firing of a rocket engine in the opposite direction slowing down the spacecraft will bring the satellite out of orbit!

36 Vocabulary Force Force Speed Speed Velocity Velocity Acceleration Acceleration Magnitude Magnitude Vector Vector Inertia Inertia Action force Action force Friction Friction Gravity Gravity Balanced forces Balanced forces Unbalanced forces Unbalanced forces Reaction force Reaction force Pressure Pressure Fluid Fluid Buoyant force Buoyant force Weight Weight Displace Displace Density Density Volume Volume Archimedes Principle Archimedes Principle


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