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Chapter 9: application of forces and transfer of energy, ((WEIGHT AND MASS…
Chapter 9: application of forces and transfer of energy
FORCES IN ANTURE THAT AFFECT US
TSUNAMI -> caused by earthquakes an volcanic eruptions can occur beneath the ocean floor strong enough to trigger a series of powerful waves
-> As waves move at high speed towards the shore with great force , the PE in the waves are converted into KE
-> resulting in erosion of shorelines , damage of buildings and loss of lives.
TROPCIAL CYCLONES -> long and intense storms in tropical regions from an increase in sea surface temperatures due to climate change
-> rapidly moving floodwaters exert forces on the soil and loosen it, resulting in landslides, strong winds can exert great forces on objects as well, towards buildings , vehicles , trees and people
VOLCANOES -> inside the earth rocks melt to form magma
-> volcanic eruption occurs when magma is pushed out towards the earth's surface with great force , a great amount of stored energy is released as heat light and kinetic energy of the magma
EARTHQUAKES -> the earths crust consists of large plates that are continually moving
-> when the plates meet , the y push against each other with great force. Occasionally, the great amount of energy is released and plates move suddenly, sudden movements are earthquakes
-> as the energy released during an earthquake can cause great damage, it would result to damage towards the surroundings above the plates
Sources of energy
HYDRO ELECTRICAL ENERGY ->the flow of water from the reservoir turns the blades of a turbine to generate electrical energy
advantages -> produces very little greenhouse gases (e.g. CO2
disadvantages -> the reservoir water floods the area behind a dam which kills plants and force animals to move to to other areas
->people who make a living through fishing may need to move as the fish most likely would relocate to a new habitat due to the water levels..?
GPE (water stored behind the dam) -> KE(water) -> KE(turbine) -> EE (generator)
SOLAR ENERGY - the energy from the sun -> can be captured by solar cells and converted into light energy into electrical energy
advantage - electrical energy can be genrate without releasing air pollutants and greenhouse gases.
disadvantage - sufficient care needed to be taken to reduce the amount of toxic waste generated during the production and disposal of solar panels.
->not really good to rely on in cold countries as the sun wont "always by there"
LE(sun) -> EE (solar cells)
GEOTHERMAL ENERGY -> it is heated stored in the earth
a geothermal power plants uses heat from deep inside the Earth to generate steam, which powers a turbine to produce a turbine to produce electricity
advantages -> Renewable and sustainable( recycled energy thru the process)
disadvantages -> requires the clearing of large areas of land which destroys the habitats of wildlife and affects the diversity of species.
HE ( earths core) -> KE (steam) -> KE (turbine) -> EE(genrator)
WIND ENERGY -> it converts the energy to wind into electricity by transferring kinetic energy to the blades of the turbine and generate electrical energy
KE (wind) -> KE( turbine) -> EE ( generator)
advantage -> renewable and sustainable( recycle the energy through the process)
disadvantages -> large plots of land have to be cleared to build wind farms -> potential loss of wildlife as natural habitats are destroyed
-> deaths of birds and bats ;-;
-> noise pollution to nearby communities (the rotation of the blades)
BIOFUELS -> energy resources from plants( sugar canes0 and animal waste
-> it is ethanol fermented form sugarcane to be used as fuel for vehicles
CPE (biofuel) -> HE( burning / surroundings?) -> KE (vehicles)
*
- ask ms pang
advantages - the plants used to make biofuels can be grown in a short time
-> can also be made into cooking oil and other food waste which helps to recycle and reduce waste
disadvantage -> CO2 produced when biofuels and burnt also contribute to global warming
NUCLEAR ENERGY -> the energy from the nucleus of the atom. Large amounts of energy is released to boil water, the steam produced powers turbines to generate electrical energy
N(nuclear)E(atom) -> HE ("boil water") -> KE (steam) -> EE (generator)
advantage -> requires less land space to generate the same amount of energy
disadvantage -> potential risks to health and safety of communities living near nuclear power plants if there is a leakage.
FOSSIL FUELS -> they are burnt and they undergo a chemical process releasing heat energy. the HE is converted into KE which is used to produce EE
CPE (fossil fuels) -> HE -> KE (turbine) -> EE (generator)
disadvantage -> burning of ffs in power stations release air pollutants and greenhouse gases into environment which contributes to global warming and increase the rate of climate changes, causing the melting of ice caps and the rising of sea levels , Hence natural disasters are to be more intense
FORCES
BASICS
forces - push or pull -> classified into contact forces and non-contact forces
Contact forces -> force that acts when a object press against each other
how to write?
->Frictional/ Elastic forces X
->Friction between (
)and the (_
)
-> the spring compression by the (
) on the (
)
Frictional Force -> force that opposes motion between two surfaces in contact.
-> e.g. climbers use chalk to absorb moisture from their hands to increase friction and improve grip on the rock wall
-> climbers wear shoes made of special type of rubber to increase the friction to push on the footholds firmly and climb up the rock wall
Elastic Force is force acting on a stretched or compressed elastic object to return to its original shape
-> e.g. Climbers use climbing ropes that can stretch and exert elastic forces which reduces impact by the climber when he falls as the rope stretches and increases the elastic force exerted
Non-contact force -> force that acts at a distance from an object.
-> e.g. gravitational and magnetic force
-> ball in the air not in contact with anything will drop due to gravitational force
Magnetic Force -> force of attraction(pull) or repulsion(push) towards magnetic materials (metal) such as steel, iron , nickel and cobalt
-> magnet two poles: north and south , like poles(N&N or S&S) -> repel
->unlike poles (N&S) attract
Gravitational force-> pulls all objects towards the earth(GF or Gravity)
gravitational force exists between any two objects with mass.
the moon exerts a GF. due to its smaller mass , its force of gravity is only about 1/6 the force of gravity of the earth. Its GF pulls on the water in the oceans, causing tides as water is a liquid and moves slightly towards the moon
weight is the measurement : unit is Newton(N)
use spring balance
Changes in state of rest or motion of an object
6 possibilities
-move a stationary object
-change direction of a moving object
-stop a moving object
-change the speed of a moving object
-change due to the turning effect of a force on an object
-> turning effect about a fixed point(pivot)
-> e.g. turning the handle of the spanner tightens the nut easily (pivot is the middle of the nut0
-change the shape/size of an object
-> the transfer of energy between objects may cause changes in the size/shape of an object
-> e.g. sponge changes shape when a force is applied to squeeze it
ATOMOSPHERIC PRESSURE -> the higher atmospheric pressure experienced at sea level , lower atmospheric pressure experienced on top a mountain
SUCTION CUP
when we press a suction cup hook against a smooth surface like a wall, air is pushed out from under the suction cup. The air pressure between the wall and the suction cup decreases and becomes lower than the atmospheric pressure. The higher the atmospheric pressure holds the suction hook in pace on the surface.
WORK DONE-> use of force to move an object in the direction of the force
there is a force acting on an object
the object moves
the object moves in the same direction as the force applied to it
answering technique : yes there is work done/ no work is done. Explain that the force applied to it is lowered or brought higher, which makes is go the direction of the force.
e.g. yes there is work done on the barbell as the weight lifter lowers the barbell dowards an
WEIGHT AND MASS-> mass is a measure of the amount of matter in an object.
-> S.I unit Kilogram(kg)
->measured on electronic balance
-> weight is a measurement of GF exerted on an object
-> S.I unit Newton(N)
-> measured on spring balance
-> may change with location
WHEN ON THE MOON
-> earth mass: 60kg , weight :600N
-> moon mass : 60kg , weight: 100N
PRESSURE = FORCE(newtons) / AREA (m2)
e.g. of pressure in everyday life : a sharp injection needle pierces the skin easily ; a high heel shoe exerts a higher pressure on the mobile phone screen than a sneaker ; a sharp knife cuts the tomato more easily than a blunt knife.
pressure in liquids
As we move deeper underwater , we feel higher pressure acting on our body.
the base of a dam has much thicker wall than its top because the water pressure is higher at the base of the dam and a thicker wall is better able to withstand higher pressure.
submariners dive to great depth underwater. The pressure deep below the water surface can be very high and a submarine needs a strong material for its structure to withstand high pressure
WORK DONE = force x distance S.I unit for work - JOULE(j)