general physics Flashcards
describe air resistance
Air resistance is a contact force. This is because it is due to the physical contact (collisions) between an object and the particles in the air.
is weight scalar
no vector
Why could the jumper reach a higher speed of he jumps from a higher altitude
The higher the altitude, the less dense air is so the diver experiences less air resistance so was able to accelerate for longer before air resistance equaled weight
Why is the window designed to have the curved shape if inside pressure is more than outside pressure
The force from air pressure acting from inside to outside is bigger than force acting inwards , keeping window in position
Why is a blue object appearing black under s red colour filter
The red colour filter only transmits red light, the blue objects absorbs the red light there is now light reflected off the blue objects and thus it appears black. Black objects absorb all wavelengths
What is the advantage of repeating measurements and calculating a mean
Reduces effect of random errors
How to work out speed of waves without the wavelength and the frequency
measure the distance travelled by a wave using a metre rule
And
measure the time taken (for the wave to travel the measured distance) with a timer
And
divide the distance by the time
Why should a thin rag be used instead of a wider ray
it is harder to judge where the centre of a wider ray is
causing a larger uncertainty (in the measurements)
increasing random errors
Describe a method the student could have used to obtain the results shown in the graph
above ( refraction and reflection)
• place a glass block on a piece of paper
• draw around the glass block
• use the ray box to shine a ray of light through the glass block
• mark the ray of light entering the glass block
• mark the ray of light emerging from the glass block
• join the points to show the path of the complete ray through the block
• and draw a normal line at 90 degrees to the surface
• use a protractor to measure the angle of incidence
• use a protractor to measure the angle of refraction
• use a ray box to shine a ray of light at a range of different angles (of incidence) • increase the angle of incidence in 10 degree intervals
• from an angle of incidence of 10 degrees to an angle of incidence of 70
degrees.
When a light wave is refracted
Velocity changes
The car aerial is connected to an electrical circuit in the car.
Describe what happens in the electrical circuit when the car aerial absorbs radio waves.
alternating) current induced (in the electrical circuit)
allow electrons vibrate / oscillate (in the electrical circuit)
The car aerial is connected to an electrical circuit in the car.
Describe what happens in the electrical circuit when the car aerial absorbs radio waves.
alternating) current induced (in the electrical circuit)
allow electrons vibrate / oscillate (in the electrical circuit)
Differences between radio waves and sound waves
- radio waves are transverse
- radio waves travel at a higher speed
- radio waves can travel through a vacuum
Why does the car have a maximum speed
The car has a maximum force forward provided by the motor causing for the speed of the car to increase, air resistance also increases until it is eventually equal in size to the forward force so car does not accelerate
Function of microphone
to convert (the pressure variations in) sound (waves) into variations in current / p.d
How does a microphone work
sound (waves) cause the diaphragm to vibrate
the diaphragm causes the coil / wire to vibrate
the coil / wire moves through the magnetic field
the coil / wire cuts magnetic field lines
a potential difference is induce
Control variable in Leslie cube practical
distance between each side (of the cube) and the (infrared) detector
Control variable in Leslie cube practical
distance between each side (of the cube) and the (infrared) detector
What is the Albedo value of a perfect black body?
Zero
The average Albedo value of the Earth’s surface is 0.3
The Albedo value of thick cloud varies between 0.6 and 0.9
At night the air at point A cools faster than the air at point B.
Explain why
At night, more radiation is emitted from the Earth than absorbed from space
cloud REFLECT radiation (towards the Earth)
allow solar radiation for radiation
at A, (there is no cloud cover so) a larger proportion of radiation will be emitted into space
How does a wave redact when it goes from deep to shallow water
velocity / speed is slower in shallow water
so edge of wave (front) entering shallow water slows down
but the part of the wave (front) in deeper water continues at a higher speed (leading to a change in direction of the wave fronts)
Why dies a wave not refract if it enters
every point on the wave (front) enters / hits the shallow water at the same time
and so every point slows down at the same time
What evidence could be used to strengthen conclusion for angle of incidence = angle of reflection
results could be collected for angles (of incidence) not yet measured
What evidence could be used to strengthen conclusion for angle of incidence = angle of reflection
results could be collected for angles (of incidence) not yet measured
Why is the induced current alternating
because the magnet changes direction
The seismometer cannot detect small vibrations.
Suggest two changes to the design of the seismometer that would make it more sensitive to small vibrations
any two from:
• stronger magnetic field
allow stronger magnet allow heavier magnet bigger magnet is insufficient
• more turns on the coil
bigger coil is insufficient
do not accept more coils of wire
• turns pushed closer together
• spring with a lower spring constant
allow less stiff spring allow weaker spring
do not accept add an iron core
Why are microwaves good for communication
can travel through the atmosphere
When radio waves are absorbed by an aerial they may create an alternating current in an electrical circuit.
If an alternating current is created what frequency would there be
Same as radio wave
Explain why the small hole looks black.
light (inside the tin can) is reflected many times before incident on the hole
at each reflection energy / light is absorbed so (very) little light / energy leaves the hole
Explain why the small hole looks black.
light (inside the tin can) is reflected many times before incident on the hole
at each reflection energy / light is absorbed so (very) little light / energy leaves the hole
Describe one piece of evidence that shows when a sound wave travels through the air it is the wave and not the air itself that travels. (separa
vibrating drum skin does not move the air away to create a vacuum (around the drum)
Explain how the loudspeaker converts current in an electrical circuit to a sound wave
the current in the electrical circuit is varying
the current passes through the coil
the coil experiences a force (inwards or outwards)
reversing the current reverses the force
the size of the current affects the size of the force
the varying current causes the coil to vibrate
the (vibrating) coil causes the cone to vibrate
the vibrating cone causes the air molecules to move
the movement of the air molecules produces the pressure variations in the air needed for a sound wave
the air molecules bunch together forming compressions and spread apart forming rarefactions
