The roller coaster The Ninja has a height of 122 ft and speed of 52 mph. Its potential energy due to height changes into kinetic energy of motion. Work is done by a force when that force causes an object to move in the direction of the force. The kinetic energy of an object is 1/2mv^2. The potential energy due to gravity is mgh. The work-energy theorem states that the work done on an object is equal to its change in kinetic energy.
This is a summary of the topic "Energy, work and power" in the GCE O levels subject: Physics. Students taking either the combined science (chemistry/physics) or pure Physics will find this useful. These slides are prepared according to the learning outcomes required by the examinations board.
This is a summary of the topic "Energy, work and power" in the GCE O levels subject: Physics. Students taking either the combined science (chemistry/physics) or pure Physics will find this useful. These slides are prepared according to the learning outcomes required by the examinations board.
A simple ppt yet interactive on the topic work power and energy. With smooth design and looks the ppt is very good for clearing the basics related to this topic, hope it will help you further.
A simple ppt yet interactive on the topic work power and energy. With smooth design and looks the ppt is very good for clearing the basics related to this topic, hope it will help you further.
ENERGY AND POWER
This ppt is from XI class CBSE board
Energy
A body which has the capacity to do work is said to possess energy.
For example , water in a reservoir is said to possesses energy as it could be used to drive a turbine lower down the valley. There are many forms of energy e.g. electrical, chemical heat, nuclear, mechanical etc.
The SI units are the same as those for work, Joules J.
In this module only purely mechanical energy will be considered. This may be of two kinds, potential and kinetic.
Power
Power is the rate at which work is done, or the rate at which energy is used transferred.
Equation 3.6
The SI unit for power is the watt W.
A power of 1W means that work is being done at the rate of 1J/s.
Larger units for power are the kilowatt kW (1kW = 1000 W = 103 W) and
the megawatt MW (1 MW = 1000000 W = 106 W).
If work is being done by a machine moving at speed v against a constant force, or resistance, F, then since work doe is force times distance, work done per second is Fv, which is the same as power.
This slide describes the idea of work and work-done and various idea and principles about energy and its utilization. It defines the basic aspects of work and how it is related to each other
2. The Ninja, a roller coaster at Six Flags over Georgia, has a height of 122 ft and a speed of 52 Mph. The potential energy due to its height changes into kinetic energy of motion.
3. WORK Work is done by force when there is a force applied on the body and the body must move with a displacement in line with the force applied. πΉ Β πΉ Β πΉ Β π Β π Β π Β πΉ Β βπ Β π= angle bet. πΉand βπ πΉ|| = component of πΉ parallel with βπ Β π Β βπ Β πΉ|| Β π=πΉ||βπ =πΉβπ cosπ Β Work done by constant force
5. Example 01 Demi horizontally pushes the 200-N crate in a rough horizontal plane with a constant force of 90 N to continuously move it in uniform motion at a distance of 100 m. What is the total work done on the crate?
6. energy Energyis anything that can be converted into work; i.e., anything that can exert a force through a distance. Energy is the capability for doing work. Unit of energy is the same to the unit of work. Other units used: calorie British Thermal Unit (Btu) kilowatt-hour
7. Kinds of Mechanical Energy Kinetic Energy, K β βspeedβ Potential Energy, U β βpositionβ or βconditionβ a. Gravitational PE, Ug b. Elastic PE c. Electric PE Transit Energies: KE and Heat β
8. Work done and Kinetic Energy π£ Β π£π Β π Β π Β βπ Β π=π£2βπ£π22βπ Β πΉ||=ππ£2βπ£π22βπ Β πΉ=ππ Β πΉ||βπ =12ππ£2β12ππ£π2 Β πΎ=12ππ£2 Β Kinetic energy β΄π=πΎβπΎπ=βπΎ Β Work-Energy Theorem Work done on the body by resultant forces is its change in kinetic energy
9. Work done by gravity (weight) and gravitational potential energy ππ€=π€βπ cosπ Β π€ Β ππ€=πππ¦βπ¦πcos180 Β βπ Β π¦ Β ππ€=πππ¦πβπππ¦ Β π€ Β π¦π Β ππ=πππ¦ Β Gravitational potential energy β΄π=ππβπ=ββπ Β Work done on the body is its negative change in potential energy
10. Review first: Work π=πΉ||βπ =πΉβπ cosπ Β πΎ=12ππ£2 Β Kinetic Energy Gravitational Potential Energy ππ=πππ¦ Β Work-Energy Theorem π=βπΎ Β
11. since π1+π2+β¦=βπΎ Β π=βπΎ Β π1=ββπ Β π2+Β β¦=Β πππ‘hππ=workΒ doneΒ byΒ otherΒ forces Β β΄Β Β Β Β Β Β Β Β Β ββπ+πππ‘hππ=βπΎ Β ππβπ+πππ‘hππ=πΎβπΎπ Β Law of Conservation of Energy πΎπ+ππ+πππ‘hππ=πΎ+π Β Initial energy = final energy
12. Examples: Use energy methods to solve all problems A bus slams on brakes to avoid an accident. The thread marks of the tires is 25 m long. If ππ=0.70, what was the speed of the bus before applying brakes? A 1.50-kg book is dropped from a height of 15.0 m from the ground. Find its potential and kinetic energy when it is 6.0 m from the ground. A small rock with a mass of 0.20kg is released from rest at point A, which is at the top edge of a large hemispherical bowl with radius R = 0.80m. Assume that the size of the rock is small in comparison to the radius of the bowl, so the rock can be treated as particle, the work done by the friction when it moves from point A to point B at the bottom of the bowl is -0.22J. What is the speed of the rock when it reaches point B? Β
13. Power Power is defined as the rate at which work is done. π·=βπΎβπ Β Power Units of Power: watt, W 1Β W=1Β J/s erg/s foot=pound per second (ft-lb/s) horsepower 1Β hp=746Β W Β
14. Power and velocity Recall average speed or constant velocity: π£=ππ‘ Β So that π=π£π‘ Β Since π=πΉπ and π=ππ‘ Β π=πΉππ‘=πΉπ£π‘π‘ Β Power at constant velocity π=πΉπ£ Β
15. Example of Power What power is consumed in lifting a 70.0-kgrobber 1.6m in 0.50 s? π=πβπ‘ Β π=πΏπ¦π‘ Β π=πππ¦π‘ Β π=(70.0Β kg)(9.8Β ms2)(1.6Β m)Β 0.50Β s Β P= 2200 W=2.2 kW
16. MORE PROBLEMS Use energy methods to solve all problems 1. Tarzan swings on a 30.0-m-long vine initially inclined at an angle of 37.0o with the vertical. What is his speed at the bottom of the swing (a) if he starts from rest? (b) if he pushes off with a speed of 4.00m/s? hint: the work done by tension is zero. 2. A 45.0-kg block of wood initially at rest is pulled by a cord from the bottom of a 27.0o inclined plane. The tension of the cord is 310 N parallel to the plane. After travelling a distance of 2.0 m , the speed of the block is 5.0 m/s. (a) what is the work done by friction? (b) what is the coefficient of friction? 3. A 750-N box is pulled in a rough horizontal plane by a motor driven cable. The coefficient of kinetic friction between the box and the plane is 0.40. (a) How much work is required to pull it 60 m at a constant speed of 2.0 m/s? (b) What power must the motor have to perform this task?