Come on People This is not rocket science

Oh, Wait Yes it is!

Newtons First Law Chapter 6 Section 2 Thursday, February 04, 2016Thursday, February 04, 2016Thursday, February 04, 2016Thursday, February 04, 2016

Force An objects movement changes in response to a force An objects movement changes in response to a force A force is a push or a pull A force is a push or a pull Can be a contact force Can be a contact force A push or a pullA push or a pull Can be a long range force Can be a long range force GravityGravity MagnetismMagnetism

Newton's First Law of Motion An object at rest stays at rest unless acted on by an outside force An object at rest stays at rest unless acted on by an outside force An object in motion stays in motion unless acted on by an outside force An object in motion stays in motion unless acted on by an outside force

Force SI unit for force is the Newton (N) SI unit for force is the Newton (N) About the force needed to lift 4 ounces of water About the force needed to lift 4 ounces of water

Newtons First Law An object in motion tends to stay in motion unless acted on by an outside force. An object in motion tends to stay in motion unless acted on by an outside force. An object at rest tends to stay at rest unless acted on by an outside force. An object at rest tends to stay at rest unless acted on by an outside force. Also known as inertia Also known as inertia

Inertia and Mass The more mass an object has the more inertia it has The more mass an object has the more inertia it has The more inertia an object has, the harder it is to change its motion. The more inertia an object has, the harder it is to change its motion. So lets look at Football Physics So lets look at Football Physics

Which would be better as a football lineman? Why?

Adding Forces The motion of an object changes only if a force is acting on it The motion of an object changes only if a force is acting on it More than one force can act on an object More than one force can act on an object If forces act in opposite directions with equal force, no motion happens If forces act in opposite directions with equal force, no motion happens Balanced Forces Balanced Forces

Adding Forces If one force is greater than the other the object will move in the direction of the larger force If one force is greater than the other the object will move in the direction of the larger force Motion only changes if forces are unbalanced Motion only changes if forces are unbalanced Motion changes in the direction of the greater force Motion changes in the direction of the greater force

Newton’s Second Law Chapter 6 Section 3

The Second Law of Motion Used to predict Motion Used to predict Motion An object acted on by an unbalanced force will accelerate in the direction of the force An object acted on by an unbalanced force will accelerate in the direction of the force This law is actually a formula This law is actually a formula

The Second Law of Motion Acceleration = Force / Mass Force = Mass x Acceleration Or

Or F=MA F=MA

Force Measured The SI Unit for Force is the Newton The SI Unit for Force is the Newton One Newton of Force will cause 1 kg of Mass to Accelerate at 1M/S 2 One Newton of Force will cause 1 kg of Mass to Accelerate at 1M/S 2 So 1N = 1M/S 2 /kg So 1N = 1M/S 2 /kg

Sample Problem A child has a mass of 71kg A child has a mass of 71kg Her Bike has a mass of 9 kg Her Bike has a mass of 9 kg They accelerated at a rate of 3.2M/S 2 They accelerated at a rate of 3.2M/S 2 How much force was applied? How much force was applied? Well, force equals mass times acceleration Well, force equals mass times acceleration So F = 80kg x 3.2M/S 2 = 256 kg/M/S 2 So F = 80kg x 3.2M/S 2 = 256 kg/M/S 2 Or 256N Or 256N

Force of Gravity Gravity is a force Gravity is a force The force of Earth’s gravity causes all objects to accelerate at the same rate when falling The force of Earth’s gravity causes all objects to accelerate at the same rate when falling The rate is 9.8M/S 2 The rate is 9.8M/S 2

NASCAR Physics “Physics is good stuff”

What in the wide, wide world of sports has this stuff got to do with racing???

Well….. In scientific terms acceleration and mass are inversely related. In scientific terms acceleration and mass are inversely related. If the force is the same (Like say from the engine) If the force is the same (Like say from the engine) The more mass you have, the less acceleration you get The more mass you have, the less acceleration you get Or the heavier the car, the slower the acceleration given the same amount of horsepower Or the heavier the car, the slower the acceleration given the same amount of horsepower

So, which would be better as a racecar driver? Why?

That was heavy! Speaking of heavy Speaking of heavy That leads us to weight That leads us to weight So wait around for the next fascinating fact So wait around for the next fascinating fact

The Bigger They Are The Harder They Fall (But Not Faster) Weight = Mass X Acceleration due to Gravity. Weight = Mass X Acceleration due to Gravity. So… So… If your mass is 60kg If your mass is 60kg 60kg x 9.8 M/S 2 = 588N 60kg x 9.8 M/S 2 = 588N In science, weight is expressed as Newtons In science, weight is expressed as Newtons

Silly Scientists!

Say What??? Because weight is the force caused by gravity acting on mass. Because weight is the force caused by gravity acting on mass. The same force is acting on you whether you are falling or standing on the ground. The same force is acting on you whether you are falling or standing on the ground.

Mass and Weight In common language mass and weight are spoken of as the same thing. In common language mass and weight are spoken of as the same thing. In zero gravity you have no weight (that’s why we call it weightless) In zero gravity you have no weight (that’s why we call it weightless) But you have the same mass. But you have the same mass. On the moon, you would have about 1/6 th of you earth weight but the same mass On the moon, you would have about 1/6 th of you earth weight but the same mass

A balance is used for measuring mass because a balance compares an object's mass to a set of standard masses

A spring scale is used for measuring weight because a spring scale measures the force of gravity pulling objects downward.

1kg of bananas weighs 9.8N on Earth. 1 kg of bananas have a mass of 1.0 kg on Earth.

1kg of bananas weighs 3.7N on Mars. 1 kg of bananas have a mass of 1.0kg on Mars (even if they're Martian bananas)

Football Physics Would the advantage be the same on the moon? Would the advantage be the same on the moon? Yes, the mass is the same, the force is caused by mass not weight. Yes, the mass is the same, the force is caused by mass not weight.

Friction A force that resists motion A force that resists motion But is essential to our lives But is essential to our lives Could you get here without friction Could you get here without friction No No Why? Why?

Without Friction… Moving is a bear

Three Types of Friction

Static Friction Why does the food not slide off the tray when the waiter starts or stops? Why does the food not slide off the tray when the waiter starts or stops? Static friction resists movement relative to the tray. Static friction resists movement relative to the tray.

Sliding Friction Will the glass make it? What will slow it down? What will make it slide better?

Rolling Friction

Air Resistance