Karteikarten
Work and Energy
Karten in diesem Stapel (58)
- 1Work doneThus, work done by a force acting on an
object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. Work has only
magnitude and no direction. - 2Work doneWhenever a force makes the body move, work is said to be done
Work is a scalar Quantity - 3Conditions necessary for work to be done(i) a force should act on an object, and
(ii) the object must be displaced - 41 Joule1 J is the amount of work done on an object when a force of 1 N displaces it by 1 m along the line of action of the force
- 5When is work done negative or positiveWork done is negative when the force acts opposite to the direction of displacement.
Work done is positive when the force is in thedirection of displacement. - 6EnergyCapacity to do work is called energy.y. The object which does the work loses energy and the object on which the work
is done gains energy - 7How does an object with energy do workAn object that possesses energy can exert a force on another object. When this happens,energy is transferred from the former to the latter. The second object may move as it receives energy and therefore do some work.Thus, the first object had a capacity to do
work. This implies that any object that
possesses energy can do work - 8Relation between work done and speedA moving object can do work. An object
moving faster can do more work than an
identical object moving relatively slow - 9Kinetic energyenergy possessed by a
moving body by virtue of its motion - 10Derive an equation for Kinetic energyThe relation connecting the initial
velocity (u) and final velocity (v) of an object moving with a uniform acceleration a, and the displacement, s is
v2 – u2 = 2*a*s
This gives
s=v2-u2/2*a
we know F = m a. Thus,
using (Eq. 11.2) in Eq. (11.1), we can write
the work done by the force, F as
w=m*a*(v2-u2/2a)
or
1/2*m*(v2-u2)
If the object is starting from its stationary
position, that is, u = 0, then
w=1/2*m*v2
It is clear that the work done is equal to the change in the kinetic energy of an object.If u = 0, the work done will be
1/2*m*v2
Thus, the kinetic energy possessed by an
object of mass, m and moving with a uniform velocity, v is
K.E = 1/2*m*v2 - 11Potential energyThe potential energy possessed by the object is the energy present in it by virtue of its position or configuration
- 12Why does An object increases its energy when raisedthrough a heightThis is because work is done on it against gravity while it is being raised. The energy present in such an object
is the gravitational potential energy - 13Gravitational potential energyThe gravitational potential energy of an
object at a point above the ground is defined as the work done in raising it from the ground to that point against gravity - 14Derive an equation for potential energyLet the work done on the object against gravity be W. That is,
work done, W = force × displacement
= m*g*h
= m*g*h
Since work done on the object is equal to
m*g*h, an energy equal to m*g*h units is gained by the object. This is the potential energy of the object.
Ep = m*g*h - 15Potential energy ----more to knowThe potential energy of an object at
a height depends on the ground level or the zero level you choose.An object in a given position can have a certain potential energy with respect to one level and a different value of potential energy with respect to another level. - 161 Kwh1 kW h = 3.6 × 106 J
1 ‘unit’
means 1 kilowatt hour. - 17LAW OF CONSERVATION OF ENERGYWhenever energy gets transformed,
the total energy remains unchanged - 18LAW OF CONSERVATION OF ENERGYAccording to this law, energy can only be converted from one form to another; it can neither be created or destroyed. The total energy before and after the transformation remains the same. The
law of conservation of energy is valid in all situations and for all kinds of transformations - 19Example of law of conservation of energyConsider a simple example. Let an object
of mass, m be made to fall freely from a
height, h. At the start, the potential energy is m*g*h and kinetic energy is zero. Why is the kinetic energy zero? It is zero because its velocity is zero. The total energy of the object is thus m*g*h. As it falls, its potential energy will change into kinetic energy. If v is the velocity of the object at a given instant, the kinetic energy would be ½m*v2. As the fall of the object continues, the potential energy would decrease while the kinetic energy would increase. When the object is about to reach the ground, h = 0 and v will be the highest.Therefore, the kinetic energy would be the largest and potential energy the least.However, the sum of the potential energy and kinetic energy of the object would be the same at all points. That is,potential energy + kinetic energy = constant
The sum of kinetic energy and potential
energy of an object is its total mechanical
energy. - 20PowerRate of doing work
or
rate of transfer of energy
The SI unit of power is Watt.It is a scalar quantity - 211 Watt1 Watt is the power of an agent which does work at the rate of 1 Joule per second
- 22Bigger unit of PowerKilo Watt , Megawatt and Horse power
1 Kw = 1000 Watts
1 Mw = 10,00,000 Watts
1 Horse power = 750 Watts - 23Average powerWe obtain average power by dividing
the total energy consumed by the total time taken. - 24COMMERCIAL UNIT OF ENERGYLet us say we have a machine that uses 1000 J of energy every second. If this machine is used continuously for one hour, it will consume 1 kW h of energy.Thus, 1 kW h is the energy used in one hour
at the rate of 1000 J s–1. ! Kwh = 1 Unit - 25Conditions for a work to be doneThe condition for a force to do work is that it should create a displacement
- 26Work done by GravityWhenever work id done against gravity,the amount of work done by the body is equal to the product of its weight and vertical distance through which it is lifted
- 27Work done acting Obliquelywhen there is an angle between the movement of the body and the direction of force applied,
W = F Cos 0 * s - 2800 is the angle between the direction of work done and direction of motion of the body
- 29When is work done positiveWhen force acts in the direction of the motion
- 30When is work done negativeWhen force acts in the direction opposite to the direction of the motion
- 31When is work done zeroWhen force acts perpendicular to the direction of the motion
- 32EnergyEnergy is the ability to do work.The amount of energy possessed by a body is the amount of work it can do. Energy is a scalar quantity
- 33How is kinetic energy measuredIt is measured as the amount of work a body can do before coming to rest
- 34Elastic potential energyThe energy of a body due to change in its shape and size is known as elastic potential energy
- 35Transformation of energyThe change of one form of energy to the other form is called as transformation of energy
- 36Give the transformation of energy in HYDROELECTRIC POWERHOUSEPotential energy
Kinetic energy
Electric energy - 37Give the transformation of energy in THERMAL ENERGYChemical energy
Heat energy
Kinetic energy
Electrical energy - 38Give the transformation of energy in GENERATORMechanical energy
Electrical energy - 39Give the transformation of energy in BULBElectrical energy
Light energy - 40Give the transformation of energy in RADIOElectrical energy
Kinetic energy
Sound energy - 41Give the transformation of energy in STEAM ENGINEHeat energy
Kinetic energy - 42Give the transformation of energy in CELLChemical energy
Electrical energy - 43Give the transformation of energy in CAR ENGINEChemical energy
Heat energy
Kinetic energy - 44Give the transformation of energy in GAS STOVEChemical energy
Heat energy - 45Give the transformation of energy in SOLAR WATER HEATERLight energy
Heat energy - 46Give the transformation of energy in SOLAR CELLLight energy
Electrical energy - 47Give the transformation of energy in FANElectrical energy
Kinetic energy - 48Give the transformation of energy in ELECTRIC LAMPElectrical energy
Light energy - 49Give the transformation of energy in MICROWAVESound energy
Light energy - 50Give the transformation of energy in ELECTRIC MOTORElectrical energy
Mechanical energy - 51Relation between Potential and Kinetic energyPE is inversely proportional to KE
and
KE + PE = constant - 52CGS unit of workerg
- 531 ev1 ev = 1.6 * 10 power -19
- 541 Calorie1 Calorie = 4.186 J
- 55Heat energyThe energy possessed by a body due to its tempareture
- 56Light energyThe energy that produces a sensation of vision in our eyes
- 57Electrical energyThe energy associated with preferred movement of charges in a wire or a solution
- 58Nuclear energyThe energy released by nuclei during fission or fusion process
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- 10 science Karteikarten am Work and Energy, erstellt von Samruddhi Pahune am 11/03/2016.
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