1.5)Work, power and energy Flashcards
Work =
Work = force x distance , J
Power
Rate of doing work
Power = work/time , Watt/ W
Power = Energy/ Time
Energy
is the ability to do work
Gravitational potential energy
Energy stored in a body due to its height from the ground
P.E = m g h
Other forms of potential energy
1.Strain/Elastic potential energy
-energy stored in a stretched string, that makes it move when it is released
2.Chemical potential energy
Energy stored in chemicals that are given out when they undergo chemical reaction
Kinetic energy
energy due to motion
K.E = 1/2 m v^2
Free fall in terms of force and acceleration
only affected by downward force of gravity and no effect of air resistance, it accelerates by 9.8 m/s^2
Free fall in terms of potential and kinetic energy
P.E up = K.E down
What happens to the K.E when object lands
Converted to heat and sound energy
Law of conservation of energy
Energy is neither created nor destroyed, but it can be changed from one form to another
Efficiency
It represents percentage of the useful output energy from total energy input
Efficiency =
Useful energy output / Total energy input x 100
OR
Useful power output/ Total power input x 100
State what is meant by 22% efficiency
The useful power output of the solar panel is 22% of the total power input
How do solar panels work
Solar panels change solar energy to electric energy
Advantages of solar panels
-clean
-Low maintenance
-No polluting gases
-Cheap to run
-Quiet
Disadvantages of solar panels
-Unattractive
-Uses land
-D.C output
-Sometimes weather goes cloudy
How do wind farms work
1.Kinetic energy of wind
2.Rotates the blades of wind mills
3.Rotates turbines
4.Drives generator
5.Generates electricity
Advantages of wind mills
-No polluting gases
-No increase in green house effect
-Uses renewable resource
-Saves non-renewable resources
Disadvantages of wind farms
1.Depends on weather
2.Visual and sound pollution
3.Land consuming
4.Bird injuries
How do hydroelectric power station work
1.Water trapped behind the dam is at higher level
2.Water falls down through pipes P.E decreases as its converted to K.E
3.Water rotates turbines
4.Turbines drive generator
5.Generator generates electricity
Advantages of hydroelectric power stations
-Renewable resource (no waste of non-renewable resources)
-No release of polluting gases
-Low maintenance cost
-Tourist amenity
-Lake may be used for fishing or source of water
Disadvantages of hydroelectric power stations
-Only suitable for hilly regions with high rainfall
-Land consuming
-Loss of habitat and villages
-Unsuitable during drought
How does petroleum or coal work
1.Fuel heats water
2.Water vaporizes forming steam
3.Steam rotates turbines
4.Turbines drives generator
5.Generates electricity
Advantages of using petroluem
-Employment of many people
-Reliable technology
-Available in many parts of world
