File Name: work energy and power formulas .zip
This set of 32 problems targets your ability to use equations related to work and power, to calculate the kinetic, potential and total mechanical energy, and to use the work-energy relationship in order to determine the final speed, stopping distance or final height of an object. The more difficult problems are color-coded as blue problems.
Power is the rate at which work is done. Mathematically, it is computed using the following equation. The standard metric unit of power is the Watt. 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. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine.
Power is the rate at which work is done. Mathematically, it is computed using the following equation. The standard metric unit of power is the Watt. 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. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine. One horsepower is equivalent to approximately Watts.
Most machines are designed and built to do work on objects. All machines are typically described by a power rating. The power rating indicates the rate at which that machine can do work upon other objects.
A car engine is an example of a machine that is given a power rating. The power rating relates to how rapidly the car can accelerate the car. If this were the case, then a car with four times the horsepower could do the same amount of work in one-fourth the time.
The point is that for the same amount of work, power and time are inversely proportional. The power equation suggests that a more powerful engine can do the same amount of work in less time.
A person is also a machine that has a power rating. Some people are more power-full than others. That is, some people are capable of doing the same amount of work in less time or more work in the same amount of time. A common physics lab involves quickly climbing a flight of stairs and using mass, height and time information to determine a student's personal power. Despite the diagonal motion along the staircase, it is often assumed that the horizontal motion is constant and all the force from the steps is used to elevate the student upward at a constant speed.
Thus, the weight of the student is equal to the force that does the work on the student and the height of the staircase is the upward displacement. Suppose that Ben Pumpiniron elevates his kg body up the 2.
If this were the case, then we could calculate Ben's power rating. It can be assumed that Ben must apply an Newton downward force upon the stairs to elevate his body. By so doing, the stairs would push upward on Ben's body with just enough force to lift his body up the stairs.
It can also be assumed that the angle between the force of the stairs on Ben and Ben's displacement is 0 degrees. With these two approximations, Ben's power rating could be determined as shown below. This is shown below. This new equation for power reveals that a powerful machine is both strong big force and fast big velocity. A powerful car engine is strong and fast. A powerful piece of farm equipment is strong and fast. A powerful weightlifter is strong and fast. A powerful lineman on a football team is strong and fast.
A machine that is strong enough to apply a big force to cause a displacement in a small mount of time i. Use your understanding of work and power to answer the following questions. When finished, click the button to view the answers. Two physics students, Will N. Andable and Ben Pumpiniron, are in the weightlifting room. Will lifts the pound barbell over his head 10 times in one minute; Ben lifts the pound barbell over his head 10 times in 10 seconds. Which student does the most work?
Ben and Will do the same amount of work. They apply the same force to lift the same barbell the same distance above their heads. Yet, Ben is the most "power-full" since he does the same work in less time. Power and time are inversely proportional. During a physics lab, Jack and Jill ran up a hill.
Jack is twice as massive as Jill; yet Jill ascends the same distance in half the time. Who did the most work? Jack does more work than Jill. Jack must apply twice the force to lift his twice-as-massive body up the same flight of stairs. Yet, Jill is just as "power-full" as Jack. Jill does one-half the work yet does it one-half the time.
The reduction in work done is compensated for by the reduction in time. A tired squirrel mass of approximately 1 kg does push-ups by applying a force to elevate its center-of-mass by 5 cm in order to do a mere 0. If the tired squirrel does all this work in 2 seconds, then determine its power.
The tired squirrel does 0. The power rating of this squirrel is found by. When doing a chin-up , a physics student lifts her What is the power delivered by the student's biceps? The work done to lift her body is. Your household's monthly electric bill is often expressed in kilowatt-hours.
One kilowatt-hour is the amount of energy delivered by the flow of l kilowatt of electricity for one hour. Use conversion factors to show how many joules of energy you get when you buy 1 kilowatt-hour of electricity. First, convert 1 kW-hr to Watt-hours. Then convert Watt-hours to 3. Since a Watt-second is equivalent to a Joule, you have found your answer. An escalator is used to move 20 passengers every minute from the first floor of a department store to the second.
The second floor is located 5. The average passenger's mass is Determine the power requirement of the escalator in order to move this number of passengers in this amount of time.
A good strategy would involve determining the work required to elevate one average passenger. Then multiply this value by 20 to determine the total work for elevating 20 passengers. Finally, the power can be determined by dividing this total work value by the time required to do the work.
The solution goes as follows:. Physics Tutorial. What Can Teachers Do My Cart Subscription Selection. Student Extras. See Answer Jack does more work than Jill. Jump To Next Lesson: Internal vs. External Forces.
Further, they are all designed with the latest academic year subject material so that any difference in the syllabus is accounted for as well. By studying from these NCERT Physics Chapter 6 Work, Energy and Power Notes for class 12 and employing sample papers, students will no difficulty be able to alleviate any tension before exams as they will be fully prepared in advance for their board exams. Together, students will be prepared to answer every type of question like subjective and objective and aim for the best in their last year of school. SelfStudys provides chapter-wise Physics Chapter 6 Work, Energy and Power revision notes as well as short keynotes for the CBSE board examination in an easy to understand and also free downloadable PDF format so students can practice it for their studies and get good marks in their board examinations. These main subjects can be very complicated for students and the revision notes for every chapter will allow them to have an expert studying pattern with which they can achieve so much better and also enjoy studying the subject. With the help of revision notes students can revise the syllabus in a concise manner.
The learning objectives in this section will help your students master the following standards:. Use the lab titled Work and Energy as a supplement to address content in this section. In this section, students learn how work determines changes in kinetic energy and that power is the rate at which work is done. Define the general definitions of the words potential and kinetic. Point out that acceleration due to gravity is a constant, therefore PE e that results from work done by gravity will also be constant. Compare this to acceleration due to other forces, such as applying muscles to lift a rock, which may not be constant.
1 cal = J. 1 J = cal. 1 HP = W (nevertheless there are many definitions). 1 kW·h = · J. Symbol Description. S.I. Unit. W. Work. J. EK.
You must have heard these terms work, energy, and power very frequently in your day to day life, like a barber cutting hair, a laborer lifting bricks and transporting them and a student studying are all said to be working.
Any force which conserves mechanical energy, as opposed to a nonconservative force. See statement of conservation of mechanical energy. Property of conservative forces which states that the work done on any path between two given points is the same. The energy of configuration of a conservative system. For formulae, see Definition of potential energy, gravitational potential energy, and Definition of potential energy given a position-dependent force.
In physics we say that work is done on an object when you transfer energy to that object. If one object transfers gives energy to a second object, then the first object does work on the second object. Work is the application of a force over a distance. Lifting a weight from the ground and putting it on a shelf is a good example of work. The simplest case of mechanical work is when an object is standing still and we force it to move.
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Free PDF download of Physics Class 11 Chapter 6 - Work, Energy and Power Formula Prepared by Subject Expert Teacher at Vedantu. To Register Online.
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