HYDROELECTRIC POWER PLANT Friction (Thermal energy) Potential Energy Mechanical Energy Electrical Energy Kinetic Energy

Warm up

HYDROELECTRIC POWER PLANT Production capacity of 12,600 MW (megawatts) and a reliable output of 75 million MW a year. Provides 25% of the energy supply in Brazil and 78% in Paraguay

Hoover Dam

Newton ’ s Laws

The cause of it all… What causes acceleration (a change in velocity) to occur? (In other words… what must be applied?) A FORCE!!!

Force What's a force? Any push or a pull on an object to put it into motion. Force can be measured by taking an object ’ s mass and multiplying it by the acceleration. F = m*a (Units for Force are Newtons: N) 1Newton= 1kg x m/s 2 Units for acceleration are= m/s 2

Force How would you plug the force equation into a power triangle??? (F=ma)

Force Re-arrange the Force equation (F=ma) to solve for mass and acceleration… m = a = Spectrum Text book pg 270 (1-3)

Force There are several types of forces acting on this moving box. What are they?

Force Friction: A force that opposes the motion between two objects in contact with each other. Q: Is it easier to push something across concrete or ice? (WHY?) A: Ice b/c there are less frictional forces.

Unbalanced Forces What would be the NET force (overall force) on the box? = 30 N What direction will the box move? Left

Force Force problems on Pg. 270 Practice #(1-3) Pg. 276 #(22-24) Pg. 697 #(76-80)

Net Force Practice Problems 1. A 1200kg truck that is traveling at 50 m/s 2 has a head- on collision with a 400kg car that is traveling at 30 m/s 2. What is the net force of the collision and which direction will the crash go? 48, Josh and I are pushing a T.V. cart down the hallway… Josh pushes with a force of 25N and I push with a force of 15N. What is the net force? 40N of force 3. I am playing tug of war with my dog… she is pulling on the rope with a force of 13N to the right and I am pulling with a force of 23N to the left. What is the net force and which direction is the rope going? 10N

Newton ’ s First LAW LAW 1 (Law of Inertia): An object at rest will remain at rest and an object in motion remains in motion unless acted upon an unbalanced force.Law of Inertia Inertia: The property of an object to resist changes in motion unless acted upon by an unbalanced force. Unbalanced force: A net force that is not equal to zero. Ex. When the car suddenly stops and your body snaps forward.

Newton ’ s Second LAW LAW 2: The unbalanced force acting on an object equals the object ’ s mass times its ’ acceleration. To accelerate the mass of an object you must apply a force! F= m x a Ex. Any time you move an object

Newton ’ s Third LAW LAW 3:For every action force, there is an equal and opposite reaction force. Ex. Hitting a homerun off of a pitcher in baseball.

Examples of Newton ’ s Laws If you are pushing an empty grocery cart with 20N of force… will the grocery cart have the same acceleration if you continue to push it at the same force of 20N when it is full. Which Law and why? A: 2 nd law. NO…the acceleration will be less once the cart is full b/c you have added mass, and a = F/m

Examples of Newton ’ s Laws What would happen if you were standing on a skateboard and threw a really heavy ball? Which law and why? A 3 rd law. : You will go backwards on the skateboard b/c the ball is pushing you with an equal and opposite force the other way. For every action there is an equal and opposite reaction.

Examples of Newton ’ s Laws If you are riding on the bus and your books are on the seat next to you… if the bus driver stomps on the brakes…where do your books go??? Which law and why? A: 1 st law. onto the floor… An object in motion stays in motion until acted on by an unbalanced force.

WORK The Transfer of Energy How does the previous investigation help us to understand how forces transfer energy?

The Transfer of Energy is called WORK Work measures the effects of a force acting over a distance. Work = F*d so… Work= energy transferred The units are N * m = Joules (J) 1 Joule= 1kg x m 2 /s 2 (F) * (d) = Work (1kg x m/s 2 x m)= 1kg x m 2 /s 2

Work and Power Warm Up 1. Who does more work - a man who lifts a large box from the ground up into the back of a truck, or a man who puts the same box on a trolley and wheels it up a ramp into the truck? A the man who lifts it B the man with the trolley C they do the same work

Work and Power Warm Up 1. Who does more work - a man who lifts a large box from the ground up into the back of a truck, or a man who puts the same box on a trolley and wheels it up a ramp into the truck? A the man who lifts it B the man with the trolley C they do the same work

Work and Power Warm Up 2. Energy and work use the same unit of the Joule because: A that is the unit chosen by the scientist named Pascal who studied heat B energy is required to do work C both measure the speed at which power is used

Work and Power Warm Up 2. Energy and work use the same unit of the Joule because: A that is the unit chosen by the scientist named Pascal who studied heat B energy is required to do work C both measure the speed at which power is used

Complete Work Practice Problems Pg

WORK Q: If you try to move a lab table with 12,000N of force and it doesn ’ t move…How much work have you done? A: NONE!!! Because… W = 0J b/c the distance was 0m and W = 12,000N* 0m = 0J