Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Classical central-force problem wikipedia , lookup
Eigenstate thermalization hypothesis wikipedia , lookup
Gibbs free energy wikipedia , lookup
Internal energy wikipedia , lookup
Relativistic mechanics wikipedia , lookup
CP Physics Name ____________________________________ Energy & Work Use the following web site to answer these questions. http://www.glenbrook.k12.il.us/gbssci/phys/Class/energy/ene rgtoc.html 1. In physics, work is defined as a _________ acting upon an object to __________ a ________________________________. 2. Statement Answer with Explanation A teacher applies a force to a wall and becomes exhausted. A book falls off a table and free falls to the ground. A waiter carries a tray full of meals above his head by one arm across the room. A rocket accelerates through space. 3. Mathematically, work can be expressed by the following equation. ________________________________ (Note in Accelerated Physics we leave off the COS ) 4. The ___________ is the unit of work. 1 Joule = 1 Newton * 1 meter 1J = 1 N * m Click on Calculating the Amount of Work Done by Forces 5. Work Done in Diagram A Show Calculation: Work Done in Diagram B Do Not Do: Work Done in Diagram C Show Calculation: 6. Free-Body Diagram A 10-N forces is applied to push a block across a friction free surface for a Forces Doing Work on the Object Amount of Work Done by Each Force displacement of 5.0 m to the right. Free-Body Forces Doing Work on the Object Amount of Work Done by Each Force Diagram A 10-N frictional force slows a moving block to a stop after a displacement of 5.0 m to the right. A 10-N force is applied to push a block across a frictional surface at constant speed for a displacement of 5.0 m to the right. A 2-kg object is sliding at constant speed across a friction free surface for a displacement of 5 m to the right. A 2-kg object is pulled upward at constant speed by a 20-N force for a vertical displacement of 5 m. 7. (6 on page) How much work is done by an applied force to lift a 15-Newton block 3.0 meters vertically at a constant speed? 8. (7 on page) A student with a mass of 80.0 kg runs up three flights of stairs in 12.0 sec. The student has gone a vertical distance of 8.0 m. Determine the amount of work done by the student to elevate his body to this height. Assume that her speed is constant. 9. A tired squirrel (mass of 1 kg) does push-ups by applying a force to elevate its center-of-mass by 5 cm. Determine the number of push-ups which a tired squirrel must do in order to do a mere 5.0 Joules of work. Click on 10. Potential Energy ________________ _______________ is the stored energy of position possessed by an object. 11. PEgrav = ______________________ PEgrav = _______________ 12. To determine the gravitational potential energy of an object, a ________ ______________ _____________________ must first be arbitrarily assigned. Typically, the ground is considered to be a position of zero height. But this is merely an arbitrarily assigned position which most people agree upon. 13. Since the gravitational potential energy of an object is directly proportional to its height above the zero position, a __________________ of the height will result in a doubling of the gravitational potential energy. A __________________ of the height will result in a tripling of the gravitational potential energy. 14. Give the potential energy at each position. A B C D E _____________ _____________ _____________ _____________ _____________ Click on 15. Kinetic Energy _____________ ______________ is the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy. 16. _________________________________________ where m = mass of object v = speed of object 17. This equation reveals that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by a factor of __________; for a threefold increase in speed, the kinetic energy will increase by a factor of __________; and for a fourfold increase in speed, the kinetic energy will increase by a factor of __________. 18. Kinetic energy is a __________ quantity; it does not have a direction. Unlike velocity, acceleration, force, and momentum, the kinetic energy of an object is completely described by magnitude alone. 19. The unit for kinetic energy is the ______________________. 20. Checking your understanding 1. Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a speed of 20.0 m/s. 2. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy? 3. Missy Diwater, the former platform diver for the Ringling Brother's Circus had a kinetic energy of 15 000 J just prior to hitting the bucket of water. If Missy's mass is 50 kg, then what is her speed? Click on Mechanical Energy 21. The energy acquired by the objects upon which work is done is known as ___________________ ___________________. 22. ___________________ __________________ is the energy which is possessed by an object due to its motion or its stored energy of position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). Click on Power ___________________ is the rate at which work is done. It is the work/time ratio. Mathematically, it is computed using the following equation. Power = _____________________________ The standard metric unit of power is the _____________. As is implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time. Thus, a Watt is equivalent to a Joule/second. For historical reasons, the ___________________ is occasionally used to describe the power delivered by a machine. One horsepower is equivalent to approximately 750 Watts. 1. Two physics students, Will N. Andable and Ben Pumpiniron, are in the weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one minute; Ben lifts the 100-pound barbell over his head 10 times in 10 seconds. Which student does the most work? Which student delivers the most power? Explain your answers. 2. During the Personal Power lab, Jack and Jill ran up the hill. Jack is twice as massive as Jill; yet Jill ascended the same distance in half the time. Who did the most work? Who delivered the most power? Explain your answers. 3. A tired squirrel (mass of 1 kg) does push-ups by applying a force to elevate its center-of-mass by 5 cm. Determine the number of push-ups which a tired squirrel must do in order to do a mere 1.0 Joule of work. If the tired squirrel does all this work in 4 seconds, then determine its power. 4. If little Nellie Newton lifts her 40-kg body a distance of 0.25 meters in 2 seconds, then what is the power delivered by little Nellie's biceps? Go To Lesson 2 Internal Forces External Forces XXXXXXXXX XXXXXXXXX XXXXXXXXX 1. Description KE to PE or PE to KE of Motion Explain A ball falls from a height of 2 meters in the absence of air resistance. A skier glides from location A to location B across the friction free ice. 2. A baseball is traveling upward towards a man in the bleachers. 3. Description KE to PE or PE to KE of Motion Explain A bungee chord begins to exert an upward force upon a falling bungee jumper. 4. 5. The spring of a dart gun exerts a force on a dart as it is launched from an initial rest position. Go To Analysis of Situations in Which Mechanical Energy is Conserved The above demonstrate the ____________________________________________