Work, Power and Energy - Physics

Work, Power and Energy - Physics | General Awareness & Knowledge - Bank Exams PDF Download

 Table of contents Work Negative Work Physics: Zero Work Physics : Law of Conservation of Energy Einstein Relation

Work

• Whenever a force acting on a body displaces it, work is said to be done.
• If a force F acting of the body displaces it by a distance s in the direction of force , work done is given by,
W = F.s (or)

W = |F||s| cosθ

Angle between Force and Displacement

• If θ < 90°, work done is positive and if θ > 90° it is negative.
•  Whenever a force acting on a body displaces it, work is said to be done.
• If a force F acting of the body displaces it by a distance s in the direction of force , work done is given by,
W = F.s (or)

W = |F||s| cosθ

• If θ < 90°, work done is positive and if θ > 90° it is negative.

Examples:

• When body falls freely under gravity, θ = 0, and work done is positive.
• When a lawn roller is pulled by applying a force along the handle at an acute angle, work done by applied force is (+) ve.
• When a spring is stretched or when a gas filled in a cylinder filled with moving piston is allowed to expand, work done is positive.

Negative Work Physics:

If θ is obtuse (θ > 90°), work done is negative.

• Examples :
• When a body is thrown up, its motion is opposed by gravity; θ between F and s is 180°.
• When a body is moved over a rough horizontal surface, the motion is opposed by the force of friction.
• Work done by the friction force is negative.
• When brakes are applied to a moving vehicle.
• When a positive charge is moved closer to another positive charge.

Zero Work Physics :

If θ is right angle (θ = 90°), work done is zero.

Examples :

• When we fail to move a heavy stone because s > = 0.
• Coollie carrying some load on his head on a horizontal platform θ = 90°.
• Person carrying a briefcase moves on a horizontal road.
• The total capacity of doing work by a body is called its energy.
• It is a scalar quantity.
• Its unit is joule.

Kinetic energy -

the energy possessed by a body by its motion is called its kinetic energy.

• K=1/2 mvjoule

Potential energy-

it is the energy stored in a body by virtue of its position of state.

• U= mgh

Law of Conservation of Energy

• It states that the total energy remains constant in any process i.e., it may neither be created nor destroyed.
• KE + PE + other forms of energy = constant
• If conservative forces are acting on a body, then,
• KE + PE = constant i.e., the loss of PE is equal to the gain in KE.

Einstein Relation

• According to Einstein, mass can be converted into energy and energy can be converted into mass. One can be obtained at the cost of the other.
• The equivalence between mass and energy is expressed in terms of Einstein relation:
• E = mc²
• Where m is the mass that disappears, E is the energy that appears and c is the velocity of light in vacuum (c = 3 x 108; m/s).
• The rate of doing work by a body is called its power.
• If an agent does work W in time t then average power is,
• P = W/t = F.s/t = F.v = |F||v|cosθ
• It is a scalar quantity.
• SI units of power is watt and is also measured in horse power.
• 1 HP = 746 W (watt)
The document Work, Power and Energy - Physics | General Awareness & Knowledge - Bank Exams is a part of the Bank Exams Course General Awareness & Knowledge.
All you need of Bank Exams at this link: Bank Exams

General Awareness & Knowledge

401 videos|542 docs|151 tests

FAQs on Work, Power and Energy - Physics - General Awareness & Knowledge - Bank Exams

 1. What is negative work in physics?
Negative work in physics refers to the situation where the force applied on an object and the displacement of the object are in opposite directions. This means that the work done on the object by the force is negative. For example, if you push a box to the left while the box moves to the right, the work done by your force is negative.
 2. What is zero work in physics?
Zero work in physics occurs when the force applied on an object and the displacement of the object are perpendicular to each other. In this case, the work done on the object is zero. For instance, if you push a box horizontally while the box moves vertically, no work is done on the box.
 3. What is the law of conservation of energy?
The law of conservation of energy states that energy cannot be created or destroyed, but it can only be transferred or transformed from one form to another. This means that the total amount of energy in a closed system remains constant over time. For example, if a ball is dropped from a certain height, its potential energy decreases as it falls, but its kinetic energy increases by the same amount.
 4. What is the Einstein relation in physics?
The Einstein relation in physics refers to the relationship between energy (E), mass (m), and the speed of light (c). According to Einstein's theory of relativity, the equation E = mc^2 states that energy (E) is equal to mass (m) multiplied by the square of the speed of light (c). This equation shows the equivalence between mass and energy, highlighting the concept of mass-energy equivalence.
 5. How are work, power, and energy related in physics?
Work, power, and energy are all related concepts in physics. Work is the transfer of energy that occurs when a force is applied to an object and causes it to move a certain distance. Power is the rate at which work is done, and it is calculated by dividing the amount of work by the time taken to do that work. Energy, on the other hand, is the ability to do work or transfer heat. It exists in various forms such as kinetic energy, potential energy, and thermal energy. The work done on an object is directly related to the change in its energy.

General Awareness & Knowledge

401 videos|542 docs|151 tests

Up next

 Explore Courses for Bank Exams exam
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

,

;