chapter 9 Flashcards
types of forces
- contact force
- non-contact force
contact forces:
- friction
- elastic force
friction definition
force that opposes motion between 2 surfaces in contact
friction example
- climbers use chalk, which absorbs moisture, increasing friction and improving their grip.
elastic force
force that allows a stretched/compressed object to return to its original shape
elastic force examples
climbing ropes: can stretch and exert elastic force. when a climber falls, the elastic force exerted increases, reducing impact
non-contact forces:
- gravitational forces
- magnetic force
gravitational force
force that attracts 2 objects towards each other
weight definition
measure of gravitational force acting on an object
magnetic force
force exerted between a magnet and another magnetic material/magnet
attraction and repulsion
- like poles repel
- unlike poles attract
magnetic force example
maglev train
- due to repulsion, the train floats slightly above the track
- reduces friction, allowing the train to travel faster
SI unite of weight
N, Newton
mass definition
amount of matter in an object
SI unit of mass
kg, kilogram
how to measure forces
spring balance
pulling a block using a spring balance, smooth VS rough surface
smooth: less force needed
rough: more force needed
weight in different location
- changes with location
mass in different location
- remains the same regardless of location
changes in state of rest/motion of an object
- move a stationary object
- stop a moving object
- change the speed of object
- change in direction in which object moves
pivot definition
the point around which the object can rotate or turn
turning effect example
removing lid of a tin can
changes in size/shape of object
- blowing up balloon
- change of shape of sponge
pressure
an effect of force acting on an object
pressure factors
- amount of force
- contact area
pressure formula
force/area = pressure
n/m2, Pa (pascal)
pressure example (needle)
- needle has to be very sharp
- surface area with skin is small
- high pressure is applied -> pierce skin easily
pressure in liquids
- the deeper we are underwater, the high the pressure
application of pressure in liquid: dam
base of dam is very thick because water pressure is higher at the base of the dam compared to the top
- when water levels rise, pressure at the bottom will increase -> thicker walls
atmospheric pressure relationship (height)
the higher we are, the less atmospheric pressure
drinking straw
- when you suck on a straw, air is removed from inside of it
- air pressure in straw decreases, becoming lower than the surrounding atmospheric pressure
- high atmospheric pressure pushes liquid up the straw and into the mouth
suction cup
- when the suction cup is pressed down, air is pushed out from under the cup
- air pressure between the surface and suction cup decreases (lower than atmospheric pressure)
- higher atmospheric pressure holds suction cup in place
work done
- when a force is applied on an object and causes it to move the same direction as the force
work down unit
joules (J)
work done conditions
- force applied on object
- object moves in same direction as force
lifting a box from the floor (work done?)
yes
carrying a box in a fixed position (work done?)
no
box is carried and moved forward (work done?)
no
check page 24 textbook
sources of energy:
- fossil fuels
- bio-fuels
- nuclear energy
- geothermal energy
- wind energy
- solar energy
- hydroelectric energy
fossil fuel:
- non-renewable
- formed from remains of dead animals/plants
fossil fuels equation
chemical potential energy
-> heat energy
-> kinetic energy
-> electrical energy
impact of fossil fuels on the environment
- releases air pollutants
- contribute to global warming
solar energy
solar panels trapping sunlight to convert to electrical energy
solar energy equation
light energy (the sun)
-> electrical energy (solar cell)
impact of solar panels
- envrionmentally friendly
- disposal/production may generate toxic waste
hydroelectric energy
electrical energy generated by turbines when moving water powers them
- stores water behind the dam
- water released powers turbines to generate electrical energy
hydroelectric energy equation
gpe (water behind dam)
-> kinetic energy (water)
-> kinetic energy (turbine)
-> electrical energy (geneator)
hydroelectric energy explained
- reservoir water stores GPE
- water runs down passageway high speed -> GPE->KE
- moving water turns blade of turbine KE of water -> KE of turbine
- KE of blades -> EE in generator
impact of hydroelectric energy
- water may flood -> kills plants and animal\
- new fishing spots
wind energy
wind turbines convert energy from wind to EE
wind energy equation
- kinetic energy (wind)
-> kinetic energy (turbine)
-> electrical energy (generator)
wind energy explained
- wind blows at wind turbine
- kinetic energy of wind is transferred to to the blades of the turbine
- blades rotate
- generator connected generates electrical energy
impact of wind energy
- large plots of land had to be cleared to build wind farms
- potential lost of wildlife/habitat
- birds may die
- nosie pollution
geothermal energy
heat stored in earth
- harnessed to generate electrical energy
geothermal energy equation
- heat energy (earth’s core)
- KE (steam)
- KE (turbine)
- EE (generator)
geothermal energy explained
- goethermal plant uses heat from deep inside earth’s core generate steam
- powers turbine
- produce energy
goethermal process
- cooled water is pumped in hot rocks inside earth’s core
- cooled water is heated by geothermal energy and turns into steam
- hot water and steam is pumped to earth’s surface
- steam is sued to power turbine and generator to generate EE
impact of geothermal
- require cleaning of land
- destroy habitats
- traces of toxic elements burried are drawn out
biofuels
- animal waste/plant materials that cannot be eated
- recycling food waste (cooking oil)
biofuels equation
- cpe (biofuel)
- heat energy
- KE (vehicle)
biofuels explained
- plants are grown
- plant (waste) used to make biofuels
- biofuels mix with other fuels + power vehicles
-carbon dioxide released when fuel burns is absorbed by plants
impact of biofuels
- burning biofuels release air pollutants
- plants used can be grown again quickly
- biofuels can be used for cooking
- reduce waste
- balance amount of CO2 released with CO2 absorbed
nuclear energy
- energy harnessed from nucleus of an atom
- obtained through nuclear reactions -> EE
nuclear energy equation
- nuclear energy (atom)
- heat energy
- KE (turbine)
- EE (generator)
nuclear energy explained
- nuclear power plants generate EE using heavy atoms
- atoms split into smaller ones, large heat is released
- used to boil water
- steam produce powers turbines to generate EE
nuclear energy impact
- health risks
- nuclear accidents
