Hello my dear Students, As you can see I am not here today. I will be back tomorrow so please don’t shed too many tears for me. I know its tough but I’m sure you can do it. I believe in you! Put all jokes aside, it is crucial for you to complete everything (both classwork and homework) that I have left for you as we will not have extra class time to spend on them. I expect everything I have left to be done when I see you next. You will be at your best behavior today. I am looking forward to hearing great feedbacks from your sub. Thank you, Ms. Dariush

Homework: 2 nd and 3 rd Block: 1.Read and annotate pages 156, 157, and Finish the 7 th Grade SOL Packet. 3.“Newton's Laws of Motion” Quiz next class. 4 th Block: 1.Complete pages 7-9 of the SOL packet. 2.“Newton's Laws of Motion” Quiz next class.

Essential Question (pg. 135): What is friction? Friction is the force that opposes motion between any two surfaces that are touching. What creates friction: It happens when two surfaces rub against each other.

Essential question (pg. 129): What is force? Energy that is created by a push or a pull Energy that is created by a push or a pull What is inertia: Object’s resistance to change in motion Object’s resistance to change in motion (objects are lazy and stubborn, if they are stationary they want to stay stationary; and if they are moving they want to keep moving. ) (objects are lazy and stubborn, if they are stationary they want to stay stationary; and if they are moving they want to keep moving. )

What is the S.I. unit for force? Newtons (N)

How it affects …. Balanced Forces Unbalanced Forces MotionKeeps the object moving Slows down or stops the object AccelerationNo acceleration Increase in the direction of larger force Net Force0>0 VelocityConstant velcity Increase in the direction of larger force

Page 131 Newton’s first law of motion: Car driving down the road: inertia: - car keeps on moving unless it is stopped by outside forces inertia: - car keeps on moving unless it is stopped by outside forces Car sudden stop (hitting a tree/ sudden break): The person in the car wants to continue moving at the speed the car was moving. The person in the car wants to continue moving at the speed the car was moving. Explanation of observation: The seat belt exerts a force against the person’s body to stop them from moving forward and flying off the seat. The seat belt exerts a force against the person’s body to stop them from moving forward and flying off the seat.

Car at rest (stop sign): Inertia- car at rest wants to stay at rest until moved by an outside force. Inertia- car at rest wants to stay at rest until moved by an outside force. Car being hit from behind: When a stopped car begins moving quickly, you are pushed back against the seat. The body is at rest, but the moving car exerts a force and changes this. When a stopped car begins moving quickly, you are pushed back against the seat. The body is at rest, but the moving car exerts a force and changes this. Explanation of observation If there was no “head rest” then the neck would snap back very hard causing a whiplash. If there was no “head rest” then the neck would snap back very hard causing a whiplash.

Newton’s second law of motion How force affects acceleration: The amount of force applied to two objects with the same mass will cause them to accelerate differently. The amount of force applied to two objects with the same mass will cause them to accelerate differently. more force will make the object move faster. more force will make the object move faster.

How mass affects acceleration: If the same force is applied to two objects with different masses, the lighter object will accelerate faster. If the same force is applied to two objects with different masses, the lighter object will accelerate faster.

Newton’s Third law: Observation: When a tennis ball hits the floor it exerts force on the floor (action) – the floor reacts by pushing the ball up with the same force (reaction) Reason: for every action there is an equal and opposite reaction.

What factors affect the amount of friction between two surfaces? Texture of surfaces Texture of surfaces Force that pushes the surfaces together Force that pushes the surfaces together Your Question: Why does friction occur? It occurs because no surface is perfectly smooth (all surfaces are bumpy, therefore the “mountains and valleys” get get stuck into each other)

Essential Question (pg. 137): What are the different forms of friction? Static friction Static friction Kinetic friction (sliding friction, rolling friction, fluid (liquids and gases) friction ) Kinetic friction (sliding friction, rolling friction, fluid (liquids and gases) friction ) Which is greater, static or kinetic friction? Static friction is greater because it keeps objects from moving.

What are all the types of friction a swimmer experiences diving through the water? Kinetic friction ( fluid friction and sliding friction) What is fluid friction? When two surfaces rub against each other and one of the surfaces is a fluid (gas or liquid)

Essential Question (pg. 139): What causes falling object to fall? Gravity Which planet has the greatest acceleration due to gravity and why? Jupiter, because it has the lowest mass (gas giant, mostly made of gases)

What happens to the gravitational force between two bowling balls if they were moved farther apart? They gravitational force between them would decrease, because the distance between them increases. Your Question: What are the two factors that affect gravity? Mass of different objects Mass of different objects Distance between the two objects Distance between the two objects

Essential Question (pg. 151): What counts as work? Work means the use of force to move an object in the same direction as force. Work means the use of force to move an object in the same direction as force. Explain why pushing on a building is not work even though you may get tired. Pushing a building is not considered work because the building does not move no matter how much you push it. Pushing a building is not considered work because the building does not move no matter how much you push it.

Why isn’t carrying a box down a hallway considered work? It is considered work because force applied to lift the box is NOT in the same direction as the box moves.

Work Equation Work = Force x distance w = F x d w = F x d Equation Symbol Symbol Meaning S.I. Unit WWorkJoules (J) FForceNewtons (N) dDistanceMeters (m)

Essential Question (pg. 153): How does increasing the power affect work and time? More work in the same amount of time More work in the same amount of time Same amount of work in shorter time Same amount of work in shorter time What are the S.I. units for power? J/s or Watts J/s or Watts

Explain how a 10 W motor in blender and a 20 W motor in a blender do work differently. It will take longer for a 10 W blender to do the same amount of work as a 20 W blender. It will take longer for a 10 W blender to do the same amount of work as a 20 W blender.

Equation Symbol Symbol Meaning S.I. Unit PPowerWatt or J/s WWorkJoules tTimeS Power Equation Power = Work / Time

Essential Question (pg. 159): How do machines help us? They make work easier by taking our work and changing it to a job. They make work easier by taking our work and changing it to a job. What three things do machines do? It takes an input work and manipulates it by either increasing the force, distance, or changing the direction the force is going to be applied. It takes an input work and manipulates it by either increasing the force, distance, or changing the direction the force is going to be applied.

Explain why machines do not lessen the amount of work you need to move a load? They change the way work is done. They either: Increase the amount of force applied Increase the amount of force applied Increase the distance over which force is applied Increase the distance over which force is applied Changes the direction the work is applied Changes the direction the work is applied

Essential Question (pg. 169): What are some types of simple machines? Lever, Pulley, inclined plane, wheel and axle, screw, wedge Lever, Pulley, inclined plane, wheel and axle, screw, wedge When will a wheel an axle have a mechanical advantage greater than one? When the input force is applied to the wheel, because the machine multiplies the input force. When the input force is applied to the wheel, because the machine multiplies the input force.

How do screws help us do work? Screws are inclined plane wrapped around a cylinder. They move objects to a greater depth (or higher elevation) by increasing the force applied to the screw.

Your Question: What is an inclined plane? It’s a simple machine that consists of a sloping surface connecting a lower elevation to a higher elevation. It’s a simple machine that consists of a sloping surface connecting a lower elevation to a higher elevation. It makes work easier by applied force over a longer distance. It makes work easier by applied force over a longer distance.