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Published byJulianne Wimpey Modified over 2 years ago

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What is Inertia? Sir Isaac Newton discovered gravity and that all objects have inertia Inertia is the tendency of an object to stay at rest or in motion Place a book on your desk. Does it move? Unless you move the book, it will remain where you put it without moving Imagine a spacecraft moving through space When the engines are turned off, the spacecraft will coast through space at the same speed in the same direction Both the book and the spacecraft have inertia Because of inertia, an object at rest tends to stay at rest An object in motion tends to keep moving at a constant speed in a straight line

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The Effects of Inertia You can feel the effects of inertia everyday Suppose you are riding in a car What happens when the car comes to a sudden stop? Your body has inertia. When the car stops, you keep moving forward- this is why we wear seatbelts! What happens when the car starts moving again? Your body tends to stay at rest when the car moves forward, and you feel like you are pushed back into your seat In baseball, inertia tends to keep a player running in a straight line This is why runners have to “round” the bases instead of making sharp turns

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Inertia and Mass The more massive an object, the more inertia it has Example: a bus would need more force to slow it down than a bicycle because the bus is more massive. The bus would also need more force to set it into motion. Therefore, the bus has more inertia. Bowling balls are made to be heavy so that once they are in motion, they will be difficult to stop Also, the greater an object’s mass and speed, the greater its momentum. Momentum is a measure of difficult it is to stop an object. Often, objects with greater inertia have greater momentum.

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Newton’s 1 st Law of Motion Newton’s 1 st law of motion explains how inertia affects moving and nonmoving objects Newton's 1 st law states that an object will remain at rest or move at a constant speed in a straight line unless it is acted on by an unbalanced force An unbalanced force is needed to move the book on your desk You could supply the force by pushing the book An unbalanced force is needed to change the speed or direction of the spacecraft This force could be supplied by the spacecraft’s engines An unbalanced force could set an object into motion or put it at rest

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Balanced and Unbalanced Forces Balanced forces are forces that are equal in size but opposite in direction If forces are equal and opposite, an object will remain at rest or in motion Unbalanced forces are forces that are not equal in size and/or direction and cause a change in motion of an object When unbalanced forces act on an object at rest, the object will move When unbalanced forces act on a moving object, the speed or direction will change

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Balanced Forces / Unbalanced Forces A.A. B.B.

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The forces of Thrust, Drag, Lift, and Weight are necessary for flight To give an airplane lift, air pressure below the wings must be greater than the air pressure above the wing. This makes the forces unbalanced, and sets the plane moving upward To keep the airplane in motion, forces of Lift, Weight, Thrust, and Drag must stay balanced How does Newton’s 1 st Law demonstrate Flight?

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Explain how the picture below demonstrates Newton’s 1 st Law of Motion _______________________________________________________________

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