Welcome to Physics Forces

Warm Up Turn to Page 44 in your notebook Read the “momentum” one-page reading On page 44 write a definition for the physics definition of momentum, based on the reading. Tape the reading into your notebook on page 46 12 minutes WHEN DONE: Get out planner

Agenda: summarize in planner Unit 3 Vocabulary Post Pasco Car Activity Newton’s Second Law

Learning Targets I can describe what a force is and where forces come from I can describe how balanced and unbalanced forces affect the motion of an object

Writing and Reading Discussion Group Work Instruction Quiet Focused Active listening On Topic Ask Questions Group Work Focus on topic Fulfill Roles Lean in Instruction Listen Take notes Raise hands

Turn to your Equations and Vocabulary Page Force a push or pull on an object in a specific direction. Forces are the result of interactions between objects. Momentum a measurement of the amount of motion an object has; the product of an object’s mass and velocity

Post Reading Questions Discuss and revise answers to assigned questions You will be presenting your answers to the class Use your forces reading and your notes to help you answer the questions 10 minutes

Share out PASCO Cars Activity

Newton’s Laws of Motion 1st Law: a moving object will keep moving and an object at rest will stay at rest unless it experiences an unbalanced force 2nd Law: the acceleration of an object depends on force and mass 3rd Law: for every action, there is an equal and opposite reaction. Or, forces come in pairs.

Forces Reading On page 45 Fold your reading in half Tape into your notebook.

Cornell Notes: The 2nd Law Turn to page 47 Topic: Newton’s Second Law Essential Question: What does Newton’s Second Law say about the relationship between force, mass and acceleration?

Learning Targets I can design, build and evaluate a device that will protect a dropped egg

Throwing Eggs

The Second Law The acceleration of an object is directly proportional to the force on the object, and inversely proportional to its mass In short: Force goes up, acceleration goes up Mass goes up, acceleration goes down We need a model we can use that will help us think about how we can do something about the force experience by an egg as it hit the ground.

The Second Law: Equation Form = F m a = —

“Its not the fall that kills you. It’s the sudden stop at the end.” -Douglas Adams

F m a — Δv Δt a = = SCENARIO 1: Mass= 1 kg Δv= 4 m/s Δt= 2 s Make the change in velocity smaller: acceleration experience by the object goes down, and the force experienced by the egg goes down Make the change in time larger: acceleration experienced by the object goes down, and the force experience by the egg goes down. SCENARIO 4: Mass= 1 kg Δv= 10 m/s Δt= 2 s SCENARIO 2: Mass= 1 kg Δv= 8 m/s Δt= 2 s

How to protect your egg Increase the time it take for the velocity to change to zero Decrease the pre-impact velocity Create a force that accelerates your egg in the opposite direction #1: This will reduce the acceleration, and thus the force #2: This will also reduce the acceleration, and thus the force #3: This will lower the overall, or net, force experience by the egg. It will accelerate the egg in the OPPOSITE direction.

Δv F m = — Δt Change in Momentum Impulse

When egg hits, the momentum change is constant F When egg hits, the momentum change is constant t t = F

Clean Up Lab supplies put away Table supplies returned to box Name tags turned in Work turned in Notebooks in backpack Scrapes recycled Stay in your seat until the bell rings