Physics Flipped Notes Take notes on this powerpoint in your journal. Title your journal: Forces and Motion

Demonstrate and calculate how unbalanced forces change the speed or direction of an objects motion

Force Any push or pull on an object Acts in pairs Measured in Newtons (N) Every force has a magnitude and direction Forces can work together or against each other Forces can be balanced or unbalanced

Vectors Lines with arrows that show direction and magnitude of a force. Length of the line shows the amount of force (magnitude) The arrow shows the direction of the force.

Balanced Forces Do not cause a change in motion Occurs when objects are at rest or traveling at a constant speed and direction.

Balanced forces

Unbalanced Forces Always cause a change in motion Occurs when there is a change in speed or direction of motion

Net Force Combination of all forces acting on an object. –Add forces working in the same direction. 2 N 8 N Net Force: = 10 N –Subtract forces that are working in opposite directions. 7 N 3 N Net Force: 7 – 3 = 4 N

Add forces acting in the same direction Example: 8 N + 6 N = 14 Newtons

Subtract forces acting in opposite directions Example: 20 N – 18 N = 2 Newtons

Net Force = 0 Forces are balanced Example: 20 N – 20 N = 0 Newtons Forces are balanced - No change in motion

Newton’s 1 st Law of Motion States that: An object at rest will stay at rest unless acted on by an unbalanced force. And: An object in motion will stay in motion at the same speed and direction unless acted on by an unbalanced force.

In other words… An object will keep doing what it is doing unless forces become unbalanced Also known as the “Law of Inertia” Inertia – An object’s tendency to resist change

Law of Inertia (1 st law)

Newton’s 2 nd Law of Motion The acceleration of an object by a force is inversely proportional to the mass of the object and directly proportional to the force applied.

In other words… The smaller the object, the greater the acceleration AND the larger the object, the smaller the acceleration. The smaller the force applied, the smaller the acceleration AND the larger the force applied the larger the acceleration.

Therefore… Force = Mass X Acceleration; F = ma Example: Force = 1,000 kg X.05 m/s/s Force = 50 Newtons

Newton’s 3 rd Law of Motion For every action, there is an equal but opposite reaction

In other words… All forces act in pairs. When one object exerts a force on a second object, the second object exerts a force back that is equal in size but opposite in direction

Newton’s 3 rd Law

Space Shuttle Launch Example: Action-Reaction

Speed How fast an object is moving Rate at which an object covers a distance Speed = distance ÷ time

Example: Calculating Speed While on vacation, Lisa Carr traveled a total distance of 440 miles. Her trip took her 8 hours. What was her average speed? Speed = distance ÷ time Speed = 440 miles ÷ 8 hours Average speed = 55 miles/hour

What’s the difference between Speed and Velocity? Velocity - The rate at which an object changes position. It’s the measurement of the rate and direction of motion.

Work Occurs when a force is used to move an object through a distance Measured in Joules(J) = Newtons/meter Work = Force (N) X Distance (m); W = Fd How much work is done if a force of 20N is used to displace an object 3m? Work = (20N) X (3m) Work = 60 Joules (J)

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