Download
1 / 27
270 likes | 471 Views
Monday. 4/12/10. Warm-Up. Mini-Lab. How high does a ball bounce?. Hold a meter stick vertically, with the zero end on the ground. Drop a tennis ball from the 50-cm mark and record the height to which it bounces.
E N D
Monday 4/12/10
Warm-Up Mini-Lab How high does a ball bounce? • Hold a meter stick vertically, with the zero end on the ground. • Drop a tennis ball from the 50-cm mark and record the height to which it bounces. • Drop the tennis ball from the 100-cm mark and record the height to which it bounces. • Predict how high the ball will bounce if dropped from the 75-cm mark. Test your prediction. • THINK IT OVER: • Observing: How does the height from which you drop the ball relate to the height to which the ball bounces?
How does the height a ball is dropped from relate to how high it bounces?
Conclusions: • The ball bounces the highest when it is dropped from the greatest height. • It never bounces as high as the initial height. 100cm 75cm 50cm
Today’s Agenda • Warm-Up: Mini-Lab – How high does a ball bounce? • Classwork: • Introduce Key Question 18 • Energy, Work, and Power Student PowerPoint • Kinds of Energy Discussion • Homework: • None! • Conclusion: • What are the two major kinds of energy?
Student ObjectiveWednesday, October 15, 2014 Students will be able to… Describe how energy, work, and power are related. Name and describe the 2 basic kinds of energy. Key Question 18… What is energy and how is it passed from one thing to another?
Energy Discussion • When you hear the word energy, what comes to mind? • How do you use the word energy? Do you often get up in the morning full of energy? If you can do something with ease, you say that you have the energy to do it. But if you are too tired, you say you don’t have enough energy. We sometimes say that certain foods will give energy. • When you dance, run, or play football or tennis, doesn’t this play take energy too? We know that it takes energy to do just about anything, whether we call it work or not.
Energy & Work Reading Lets find out what energy & work are: When wind moves a leaf, or even a house, it causes a change. In this case, the change is in the position of the object. Recall that work is done when a force moves an object through a distance. The ability to do work or cause change is called energy. So the wind has energy. When an object or organism does work on another object, some of its energy is transferred to that object. You can think of work, then, as the transfer of energy. When energy is transferred, the object upon which the work is done gains energy. Energy is measured in joules—the same units as work. WHAT IS WORK? …the transfer of energy
Energy & Work Wind blowing leaves Wind blowing down a house The position of the object has changed! Work is done when a force moves an object through a distance. • Energy is the ability to do work or cause change Vocabulary: Write this down!
ENERGY TRANSFERS Wind loses energy Leaves gain energy • When an object or organism does work on another object, some of its energy is transferred to that object. • Work is the transfer of energy Vocab: Write this down!
Power Reading Lets find out what power is: A car does work to accelerate from rest. Some car engines do this work rapidly, while others do it more slowly. The faster an engine can do an amount of work, the more power the engine has. Power is the rate at which work is done or the amount of work done in a unit of time. When you carry an object up some stairs, you do the same amount of work whether you walk or run up the stairs. (Work is the weight of the object times the height of the stairs.) But you exert more power when you run because you are doing the work faster. WHAT IS POWER? …how fast work is done
Some car engines accelerate rapidly, while others do it more slowly. Which car has more POWER? Vocab: Write this down! • Power is the rate or speed at which work is done Which person is exerting more POWER?
ENERGY NOTES Part 1: Energy, Work, and Power • ENERGY – the ability to do work. • WORK – the transfer of energy (when a force moves an object through a distance). • POWER – the rate at which energy is transferred (work is done).
Work, Energy, and Power are related… • Work is the transfer of energy. • Power is the rate at which energy is transferred What happens when a bowling ball hits bowling pins? The ball does WORK on the pin and transfers some energy to it. How can you judge how much power is involved? Observe how far and how fast the pins move.
All energy is either… kinetic energy OR potential energy
- What Is Energy? Kinetic Energy • Kinetic energy increases as mass and velocity increases.
- What Is Energy? Potential Energy • Gravitational potential energy increases as weight and height increase.
ENERGY NOTES Part 2: Two KINDS of Energy • The two main kinds of energy are KINETIC ENERGY and POTENTIAL ENERGY. • Kinetic Energy (KE) is energy of motion. • Affected by mass and velocity (1/2 m x v2) • Increased mass or velocity increases KE. • Potential Energy (PE) is stored energy. • Gravitational PE affected by mass and height • Increased as mass or height increases PE. • Elastic PE associated with objects that can be stretched or compressed. • Increased stretch or compression increases PE.
HOMEWORK NONE!!! Always copy daily homework into your agenda.
??? What are the two KINDS of energy? • Gravitational and Elastic • Gravitational and Potential • Kinetic and Elastic • Kinetic and Potential
Conclusion 26 25 Answer Now A baseball pitcher and a softball pitcher throw their ball at the same speed to a catcher. Which ball has more kinetic energy? • The baseball has greater kinetic energy. • The softball has greater kinetic energy. • They have the same kinetic energy.
