Work And Energy
Main Concepts
Work- Work is caused when we apply force on an object and the object
moves in the direction of force. Work is not caused if we are applying
force on an object but it is not moving. Work= Force x Distance.
Energy- Energy is our or anyone’s ability to perform a task. Without
energy work cannot by caused because force takes place with the help
of energy.
Power- Power means the amount of time in which work takes place. The
more the power the less the time taken to perform a work. For example-
Two people push a box, 1st person reaches the destination before than
2nd person. So, 1st person used more power.
10 Key Facts
Kinetic Energy = ½ mv² (motion energy)
Potential Energy = mgh (height energy)
Mechanical Energy conserved (KE ↔ PE)
1 Joule = 1 Newton × 1 meter
1 Watt = 1 Joule/second
Commercial unit = 1 kWh = 3.6 million J
Rate of work = Power
Law: Energy can’t be created/destroyed
Bulb rating = Power (60W = 60J/s)
Water → turbine → electric = energy forms
6 Exam MCQs
1. Work = ? (a) F×d ✓ (b) F/d
2. Moving object energy: (a) KE ✓ (b) PE
3. Height energy: (a) KE (b) PE ✓
4. 1 kWh = ? (a) 3.6×10^6 J ✓ (b) 3600 J
5. Power unit: (a) Joule (b) Watt ✓
6. Energy conserved: (a) created (b) transformed ✓
Quick Revision
Trick: Work(F×d) Energy(ability) Power(speed)
Main Concepts
Work- Work is caused when we apply force on an object and the object
moves in the direction of force. Work is not caused if we are applying
force on an object but it is not moving. Work= Force x Distance.
Energy- Energy is our or anyone’s ability to perform a task. Without
energy work cannot by caused because force takes place with the help
of energy.
Power- Power means the amount of time in which work takes place. The
more the power the less the time taken to perform a work. For example-
Two people push a box, 1st person reaches the destination before than
2nd person. So, 1st person used more power.
10 Key Facts
Kinetic Energy = ½ mv² (motion energy)
Potential Energy = mgh (height energy)
Mechanical Energy conserved (KE ↔ PE)
1 Joule = 1 Newton × 1 meter
1 Watt = 1 Joule/second
Commercial unit = 1 kWh = 3.6 million J
Rate of work = Power
Law: Energy can’t be created/destroyed
Bulb rating = Power (60W = 60J/s)
Water → turbine → electric = energy forms
6 Exam MCQs
1. Work = ? (a) F×d ✓ (b) F/d
2. Moving object energy: (a) KE ✓ (b) PE
3. Height energy: (a) KE (b) PE ✓
4. 1 kWh = ? (a) 3.6×10^6 J ✓ (b) 3600 J
5. Power unit: (a) Joule (b) Watt ✓
6. Energy conserved: (a) created (b) transformed ✓
Quick Revision
Trick: Work(F×d) Energy(ability) Power(speed)
