Improvements Have students identify lots more force pairs & do more problems These last 3 sections…this hole chapter…is pretty disjointed  Use physics classroom online more!

Bell Work 5/8/13 Turn in lab if you’re done! (+1) 1.Alyssa pushes a 5.0 kg ball with a force of 22.5 N. What will the ball’s acceleration be?

Today you are going to…take notes on Newton’s 3 rd Law of Motion. So you can…further understand forces & motion You’ll know you’ve got it when you can State Newton’s 3 rd Law Identify force pairs Give motion & no motion examples Why don’t both objects always accelerate? Why don’t both objects have the same acceleration? Calculate accelerations.

Newton’s 3 rd Law For every action force, there is an equal and opposite reaction force. OR Forces occur in equal and opposite pairs.

Newton’s 3 rd Law My hand pushes up on the eraser.My hand pushes up on the eraser. The eraser pushes down on my hand.The eraser pushes down on my hand. If the force on the eraser is 5 Newtons upward, what is the other force?

Newton’s 3 rd Law Identify force pairs

Newton’s 3 rd Law Cat-a-pult sitting on desk Shuster pushing on wall Hand pushing game! Cat-a-pult launching golf ball Which happens first?

Newton’s 3 rd Law It can make stuff move!!

Newton’s 3 rd Law to the rightSarah pushes to the right on the wall. to the leftThe wall pushes to the left on Sarah. If Sarah pushes to the right with 110 N of force, what is the magnitude and direction of the other force? If Sarah is on roller skates and has a mass of 55 kg, what will her acceleration be? What will the wall’s acceleration be? Why?

Newton’s 3 rd Law to the rightSarah pushes to the right on the wall. to the leftThe wall pushes to the left on Sarah. If Sarah pushes to the right with 110 N of force, what is the magnitude and direction of the other force? If Sarah is on roller skates and has a mass of 55 kg, what will her acceleration be? What will the wall’s acceleration be? Why?

Newton’s 3 rd Law In an action/reaction pair, why does one object sometimes accelerate while the other doesn’t?

Flyboard Video Flyboard –What are the action/reaction forces? m4Bm3cs9TFo&feature=endscreenhttp:// m4Bm3cs9TFo&feature=endscreen

Newton’s 3 rd Law If they’re equal and opposite forces, why don’t action/reaction forces cancel out???

Big Jim & Tiny Tina are ice skating close together. Big Jim says something Tiny Tina finds insulting. She pushes him with a force of 80.0 N. Calculate their acceleration.

Who accelerates more? Why? Were the forces really equal and opposite?

Newton’s 3 rd Law on Ice If Big Jim & Tiny Tina are ice skating. They push off from one another. Describe their acceleration. –They both experience the same force. –Tiny Tina accelerates more because she has less mass (inertia).

Bell Work 4/22/13 1.State Newton’s 3 rd law. (c.s.) 2.Vinny kicks a board. Identify the pair of forces. 3.Why don’t action/reaction forces cancel out? 4.W5SAYWoS

Schedule Thursday –Newton’s 3 rd Law notes Friday –Newton’s 3 rd Law notes Monday –Finish Newton’s 3 rd Law notes –Newton’s 3 rd Law questions (homework) Tuesday –Review Newton’s 3 rd Law questions –Begin Racecar Project Wednesday –Build racecar Thursday –Test racecars Friday –Newton’s 3 rd Law quiz –Work, power, & machines

Bill and Sarah are ice skating. Bill has a mass of 155 kg and Sarah has a mass of 65.0 kg. Sarah pushes off of Bill with a force of 88.0 Newtons. Calculate Bill’s acceleration AND Sarah’s acceleration. In the above problem, Bill and Sarah started off standing still, so their initial velocity was 0 m/s. If Sarah pushed for seconds, calculate her velocity & his velocity using the acceleration equation.

Newton’s 3 rd Law downAllison pushes down on the ground. upThe ground pushes up on Allison. If Allison pushes with N of force, what is the magnitude and direction of the other force? If Allison has a mass of 61 kg, what will her acceleration be? What will the Earth’s acceleration be? mass of Earth = × kilograms

If Allison pushes with N of force, what is the magnitude and direction of the other force? If Allison has a mass of 61 kg, what will her acceleration be? What will the Earth’s acceleration be? mass of Earth = × kilograms

Chuck Norris Fact When Chuck Norris does a push up, he’s not pushing himself up. He’s pushing the Earth down.

Newton’s 3 rd Law Why don’t both objects have the same acceleration?

More or Less?

Video! Steve Spangler Newton’s 3 rd Law Video 2:20 (propels himself using 3 rd Law)Steve Spangler Newton’s 3 rd Law

Shooting a gun Astronaut pushes off of spacecraft

Why don’t both objects have the same acceleration? Forces occur in equal and opposite pairs. They don’t cancel out because the forces are acting on two different objects. The result of the forces is not the same because: –The objects have different masses, so the same force results in different acceleration. –There are often other forces acting on the objects.

Bell Work Sit in your seat & get your hw out. Schedule: –Collect HW –Review for tomorrow’s quiz –Launch cars Distance to beat is 15.9 m