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physics 1
Fichas del conjunto (52)
- 12 formulas for wave speedwave speed = frequency * wavelength
wave speed = distance / time - 2formula for resultant forceforce in newtons = change in momentum in kg m/s divided by time in seconds
- 3Name four factors that can influence the stopping distance of a vehicle.Stopping distance = Thinking distance + Braking distance. The longer a car takes after seeing a hazard until stopping, the more likely an accidental collision.
THINKING DISTANCE:
thinking distance is the distance the car travels in the driver's REACTION TIME.(1)
Things that influence reaction time are: tiredness, distractions, drugs, alcohol
BRAKING DISTANCE
is affected by:
the amount of friction between the tires and the road surface (1), (which can be affected by leaves, ice, water, sand, or the baldness of the tires)
or the condition of the brakes (1)
SPEED
The other thing that influences distance is the SPEED that the vehicle is travelling at(1). The faster the vehicle is traveling, the longer the braking or thinking distance will be. - 4formula for powerpower = energy used / time take
- 5formula for efficiency100% * useful energy transferred by the device / total energy supplied to the device
- 6—
- 7State the advantages and disadvantages of a small portable petrol-powered generator when compared to a wind-powered generator.ADVANTAGES
portable (1)
not weather dependent (1)
takes up less space (1)
DISADVANTAGES
less efficient (1)
fossil fuel is polluting (1)
fossil fuel is not renewable (1) - 8formula for change in gravitational potential energychange in gpe = mass in kg * gravitational field strength in N/kg * change in height in meters
- 9State two non-renewable power sources and two of their shared disadvantages.Fossil fuels (coal, oil, gas)
Nuclear power
They both will run out and they pollute. - 10What are bio-fuels?Bio-fuels are renewable energy resources created from either plant products or animal dung. They can be solid, liquid, or gas and can be burnt to produce electricity or to run cars in the same way as fossil fuels.
- 11Discuss the advantages and disadvantages of solar power.ADVANTAGES
Solar power can be used in remote places without connection to a power station. Solar power makes no pollution to run. There are no running costs.
DISADVANTAGES
Solar panels use a lot of energy to make. They are mainly able to generate electricity on a small scale, eg for homes.
They work better in sunny places.
They don't work at night. - 12Explain the benefits and disadvantages of replacing the power station with a wind farm.ADVANTAGES
Wind farms produce no pollution, which is much better for the environment than burning coal (1). They are also cheap to run, as there are no fuel costs and minimal running costs (1).
DISADVANTAGES
You would need lots of turbines to get the same power as a coal power station (1). People nearby might also dislike the wind farm, because wind farms spoil the view and can be noisy (1). - 13What are the wavelengths of the spectrum of visible light?740nm (red) to 420nm (violet)
- 14List the known types of radiation, in order of decreasing wavelengthAM Radio (100m)
FM Radio/TV (1m)
Radar/Microwaves (1cm)
Infrared (0.01cm - 1000nm)
Visible light (640nm-420nm)
Ultraviolet (420nm-10nm)
X-rays (10nm-0.01nm)
Gamma Rays (0.01nm-0.0001nm) - 15What is an average human walking speed? Give your answer in km per hour and meters per second.average human walking speed
= 5 km per hour
= 1.6m per second - 16Will there be more radiation inside or outside the earth's atmosphere? Why?There will be more radiation outside, because radiation is ABSORBED by the Earth's ATMOSPHERE
- 17Which way do waves bend when they enter a more optically dense medium?towards the normal
- 18What is refraction?The change in direction of a wave as it travels from one medium to another.
- 19Are electromagnetic waves transverse or longitudinal?Transverse
- 20What type of electromagnetic waves are used in television remote controls?Infrared
- 21Visible light from the Sun takes the same time to reach the Earth as ultraviolet radiation from the Sun. Explain this observation.Visible light and UV radiation are both examples of electromagnetic waves. All electromagnetic waves travel at the same velocity through a vacuum or air.
- 22What is the difference between transverse and longitudinal waves? Give an example of each.In a TRANSVERSE wave, the oscillations are PERPENDICULAR to the direction of energy transfer. Example - the ripples on the surface of water.
In a LONGITUDINAL wave, the oscillations are PARALLEL to the direction of energy transfer. Longitudinal waves show areas of COMPRESSION and RAREFACTION. Example - sound waves travelling through air. - 23Explain the four properties of waves: Amplitude Wavelength Frequency PeriodAmplitude - the maximum displacement of a point on a wave away from its undisturbed position
Wavelength - the distance from a point on one wave to the equivalent point on the adjacent wave
Frequency - the number of waves passing a point each second
Period - the time for one complete wave to pass a fixed point. - 24Four waves pass a point in one second. What is the period of the wave?0.25 seconds
- 25Define and name at least two examples of 1) a scalar quantity 2) a vector quantitySCALAR:
measure magnitude
ex. speed, distance, mass, temperature
VECTOR
measure magnitude and give direction
ex. force, velocity, displacement, weight, acceleration, momentum - 26A cork is floating on some water. Explain how this arrangement can show whether waves on the water surface are transverse or longitudinal.make wave (on water
surface) (1)
{look at / observe}
movement of cork (1)
if cork and wave move in
same directions, wave is
longitudinal (1)
if cork and wave move at
right angles then wave is
transverse (1) - 27Imagine that waves are approaching the shallow end of a pool, at an angle. In the shallow water, the wave speed is less than in the deep water. The frequency remains the same. Explain what happens to the direction and the wavelength of these waves when they pass from the dep water into the shallow water.WAVELENGTH
wavelength decreases, because speed decreases
wave speed = frequency * wavelength
wave speed is proportional to wavelength (at constant frequency)
DIRECTION
direction changes towards the NORMAL (the normal is at 90° to the boundary between the two media), because speed decreases - 28What is refraction?Refraction is the change of direction of light as it passes from one medium (substance) to another. The two media must have different densities, such as air and glass.
- 29What happens when light passes into a less dense medium?When light passes into a less dense medium, it speeds up. The rays bend away from the normal. This means that the angle of refraction is greater than the angle of incidence.
- 30What happens when light passes into a denser medium?When light passes into a denser medium, it slows down. The rays bend towards the NORMAL (the normal is at 90° to the boundary between the two media). This means that the angle of refraction is smaller than the angle of incidence.
- 31A ball is dropped from height h above the ground. The speed of the ball just before it hits the ground is 5m/s. Calculate h. (assume acceleration due to gravity = 10m/s2)use the formula
(final velocity squared) minus (initial velocity squared)
equals
2 times (acceleration) times (distance)
a=10m/s, v=5m/s, u=0 m/s
h=(v2-u2)+2a
h=(25-0) + 2(10)
h=1.25m - 32Describe the composition of the earth, from the outside toward the center.The Earth is almost a sphere. These are its main layers, starting with the outermost:
crust - relatively thin and rocky
mantle - has the properties of a solid, but can flow very slowly
outer core - made from liquid nickel and iron
inner core - made from solid nickel and iron - 33What is the lithosphere?The Earth's lithosphere is the rigid outer layer that is made up of the crust and the part of the mantle just below it. The lithosphere is made up of a mixture of minerals.
- 34Explain how some of the properties of P-waves and S-waves lead to the present model of the Earth's interior.mention of P- being longitudinal
mention of S- being transverse
RELFLECTION: UNCHANGING SPEED
humans send sound waves to measure the thickness of Earth’s crust and detect boundary layers e.g. mantle and (outer) core
CHANGING SPEED: REFRACTION
When waves refract it can increase our understanding of change in density of rocks (in the Earth’s
interior) by detecting boundary layers of different densities - eg mantle and (outer) core
P-waves, which are LONGITUDINAL, can travel through solids AND liquids
shadow zone /absence of P-waves on side of the Earth
{transverse /S-} can {only travel through solids/not
travel through liquids}
shadow zone /absence of S-waves on opposite side of the
Earth (to source of the S-waves)
idea of internal volumes of liquid/idea of liquid (outer) core - 35What is a refracting telescope? How does it work? What did Galileo see using a refracting telescope, and why was this significant?The OBJECTIVE LENS (1) collects light (1)
and focuses/converges/refracts the light (1), producing a REAL IMAGE (1) at the FOCAL POINT (1).
The image is viewed by the eyepiece lens (1). The eyepiece produces a VIRTUAL IMAGE (1).
Galileo saw the moons of Jupiter through a refracting telescope, thus proving that not everything revolves around the earth and that the GEOCENTRIC model of the universe was not correct. - 36What is a typical speed for an airplane?250 m/s
900 km/h
560 mph - 37What is a typical speed for a car on a motorway or highway?31 m/s
112 km/h
70mph - 38What are safety features in vehicles designed to do? Give three examples.Saftety features in vehicles are designed to INCREASE COLLISION TIMES, which REDUCES THE FORCE, and so reduces the risk of injury. For example, SEAT BELTS stretch slightly and AIR BAGS slow you down gradually. CRUMPLE ZONES are areas at the front and back of a vehicle which crumple up easily in a collision, increasing the time taken to stop.
- 39What is Newton's first law of motion?A resultant force is needed to make something start moving, speed up, or slow down.
If the resultant (or net) force on a stationary object is zero, the object will remain stationary. If the resultant force on a moving object is zero, it will continue moving at the same velocity.
A non-zero resultant force will always produce acceleration or deceleration in the direction of the force. - 40What is Newton's second law of motion?Force = Mass x Acceleration
- 41Find the resultant force needed to accelerate an 80kg man on a 10kg bike at 0.25 m/s2F=ma
=(80+100) x 0.25
=22.5N - 42How is mass measured (in what units and with what instrument?) How is weight measured? What formula relates the two?Mass is measured in KILOGRAMS with a MASS BALANCE
Weight is measured in NEWTONS using a CALIBRATED SPRING BALANCE
Weight = mass (kg) x gravitational field strength (N/kg) - 43Why is it better to use a light gate instead of a stopwatch to measure short time intervals?Light gates are the best option for short time intervals. When using a stopwatch, there can be human error caused by reaction times.
- 44State why a rocket continues moving through space after turning off its thrusters.There is zero resultant force acting on the rocket (as there is no force from the thrusters or from friction)
- 45What is Newton's third law?When two objects interact, the forces they exert on each other are equal and opposite.
- 46A full shopping trolley and an empty one are moving at the same speed. Explain why it is easier to stop the empty trolley than the full trolley over the same amount of time.An object with a smaller mass will have a smaller inertial mass, so less force is needed to stop it.
- 47What is inertial mass?An object's inertial mass measures how difficult it is to change the velocity of an object.
inertial mass = force/acceleration - 48What is momentum?All MOVING objects have momentum (p). It is the product of the object mass and velocity.
p=mv
Momentum is a vector quantity. - 49What is CONSERVATION OF MOMENTUM?In a closed system, the total momentum before an event is the same as after the event.
- 50Calculate the momentum of a 60kg woman running at 3m/sp=mv
60kg*3m/s = 180kg*m/s - 51Describe how momentum is conserved by a gun recoiling (moving backwards) as it shoots a bullet. (4 marks)Before the gun fires the bullet, the total momentum is zero (neither the gun nor the bullet are moving) (1). When the bullet leaves the gun, it has the momentum in one direction (1). The gun moves backwards, and has an equal but opposite momentum to the bullet (1). This means that the total momentum after the bullet has been fired is still zero--momentum has been conserved (1).
- 52formula for kinetic energy storeKE = 1/2 * m * v2