Forces and Newton’s 3 Laws Chapter 4 Forces and Newton’s 3 Laws

Chapter 4 Objectives Warm-Up We will learn about forces by drawing free-body diagrams and using F=ma We will discuss inertia and equilibrium We will discuss and use weight and friction formulas What does force mean to you?

Forces Contact Field Needs physical contact Does not need physical contact Ex: gravity or magnetic

Vector vs Scalar Vectors Scalar Have direction and magnitude Ex: force Scalar Magnitude only Ex: time, area, volume

Free body diagram A man pulls a sled with a child on it. Draw a free-body diagram for the situation. The forces are: 60N by the string, 90N upward by the ground, 130N by Earth(gravity)

Exit Ticket and HW Draw a free-body diagram for a car colliding with a wall HW pg 124 1a and #2

Chapter 4 Objectives Warm-Up We will learn about forces by drawing free-body diagrams and using F=ma We will discuss inertia and equilibrium We will discuss and use weight and friction formulas Give two examples of field forces that you experience everyday

Review HW

Lab

Exit Ticket and HW ET- included in lab HW none for today

Chapter 4 Objectives Warm-Up We will learn about forces by drawing free-body diagrams and using F=ma We will discuss inertia and equilibrium We will discuss and use weight and friction formulas If a car moves at 60mph, how fast are the people inside going? If the car hits an object and comes to rest, how fast are the people going?

Newton’s Law of Inertia FIRST LAW An object at rest stays at rest unless acted on by a nonzero force, an object in motion stays in motion unless an outside equal but opposite force acts on it. The more mass an object has, the greater its inertia and the more force it takes to change its state of motion.

Mechanical Equilibrium Static Dynamic- push force = friction Object at rest When you stand up there is a gravitational force and a normal (support force) which will = 0 Object moving at constant speed in a straight line A car moving on a straight road at a constant speed of 45 mph.

Inertia A book on a desk at 35o and picture Pg 128 1-3

Exit Ticket HW Pg 129 1-5

Newton’s 2nd and 3rd Law 2nd Law is: F=ma Newton’s 3rd Law: If two objects intereact, the magnitude of the force exerted on object 1 by object 2 is = to the magnitude of the force exerted on object 2 by object 1 and they are opposite. (for every action there is an equal but opposite reaction) https://www.youtube.com/watch?v=ldcj5CFO8VE

THE NEWTON’S THIRD LAW

Forces always exist in pairs The basis for the Newton’s Third Law

ACTION - REACTION pair = forces that objects exert on each other THE NEWTON’S THIRD LAW ACTION - REACTION pair = forces that objects exert on each other

ACTION - REACTION pair = DO NOT cancel each other

Practice Pg 134 1-5

Exit Ticket and HW HW pg 132 1-5

Chapter 4 Objectives Warm-Up We will learn about forces by drawing free-body diagrams and using F=ma We will discuss inertia and equilibrium We will discuss and use weight and friction formulas How are we working our block day?

Agenda Check HW Pg 139 2 and 3 Pg 140 Pg 141 1 and 3

Exit Ticket and HW Study