Mind Map of Work and Energy - Pratap Sanjay Sir
Work
→ When a body is displaced by applying a force, work is said to be done.
→ Work requires energy.
eg:- 1.In animals: Energy is supplied by food.
2.In machines: Energy is supplied by fuel.
Unit of Work
SI unit: Joule (J)
1 Joule: Work done when a force of 1 Newton displaces an object by 1 meter in the direction of the force.
Work Done on an Object
➥ Work done on an object is defined as the product of the magnitude of the force acting on the body and the displacement in the direction of the force.
Conditions for Work to Be Done:
- A force must be applied.
- The object must be displaced.
- The displacement must have a component in the direction of the force.
Negative, Positive, and Zero Work
- Positive Work: When the force and displacement are in the same direction.
- Negative Work: When the force and displacement are in opposite directions.
- Zero Work: When there is no displacement or displacement is perpendicular to the force.
Work done by a spring
Units of work done
Energy
Mechanical Energy
➥ Mechanical Energy is the total energy possessed by an object due to its motion and position.
➥ It is the sum of two forms of energy:
- Kinetic Energy (K.E)
- Potential Energy (P.E)
Kinetic Energy
➥ Objects in motion possess energy and can do work. This energy is called Kinetic Energy.
Formula: K.E = ½ mv²
Work-Energy Theorem
Potential Energy
➥ Energy can get stored in an object when work is done on it.
Formula: P.E = mgh
Gravitional Potential Energy
Law of Conservation of Energy
➥ Energy can neither be created nor destroyed but can be transferred from one form to another.
➥ The total energy of an isolated system remains constant.
Conversion of Potential & Kinetic Energy
Power
➥ The rate of doing work or transfer of energy.
Formula: Power = Work / Time
Commercial Unit of Power
➥ The commercial unit of power is kilowatt-hour (kWh).
1 kWh = 3.6 × 106 Joules
Solved Numericals
Numerical on Work:
A force of 10 N displaces an object by 5 m in the direction of the force. Calculate the work done.
Solution: Work = 10 × 5 = 50 J
Numerical on Kinetic Energy:
A body of mass 2 kg is moving with a velocity of 3 m/s. Find its kinetic energy.
Solution: K.E = ½ × 2 × 3² = 9 J
Numerical on Potential Energy:
A 5 kg object is placed at a height of 10 m. Calculate its potential energy.
Solution: P.E = 5 × 10 × 10 = 500 J
Numerical on Power:
If 200 J of work is done in 10 seconds, calculate the power.
Solution: Power = 200 / 10 = 20 W
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