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GCSE Physics OCR B > P5 > Flashcards

P5 Flashcards

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1
Q

What is a satellite?

A

An object that orbits a planet in space that is either natural or artificial

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2
Q

What is centripetal force?

A

It acts towards the centre of a circle and keeps an object moving in a circle. It is provided by gravity and keeps satellites in orbit.

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3
Q

In what way does gravitational force change?

A

The gravitational force between two objects gets weaker as the objects are moved further apart. As the distance doubles the force drops by 1/4 (is divided by 4) - this is the inverse square law.

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4
Q

What is the name for the amount of time it takes a satellite to orbit an object one and when does this number change?

A

Orbital period. It increases with distance away from the object (I.e. Height from earth)

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5
Q

What does the height of an artificial satellite change?

A

It’s orbital period and the things it can be used for

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6
Q

What are the properties of a satellite in low polar orbit?

A

They go quickly, travel around earth several times daily (stronger force of gravity), travel pole to pole.
Are used to image earths surface, forecast weather and for spying

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7
Q

What are the properties of a geostationary satellite?

A

Orbit high, take 24hrs to complete an orbit (weaker force of gravity and have longer to travel), remain in a fixed position on earths equator.
Used for communications (TV) and weather forecasting

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8
Q

Why does a satellite stay in orbit?

A

Centripetal force, it would naturally travel straight but gravity causes it to continually accelerate to earth and the forces balance

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9
Q

What is a scalar quantity? Name four examples

A 
A quantity with only a size
Mass
Energy
Speed
Time
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10
Q

What is a vector quantity? Name four examples

A 
A quantity with a size and a direction
Weight
Velocity
Force
Acceleration
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11
Q

What is relative speed?

A

The combined velocity of two objects

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12
Q

Does a projectile launched horizontally have a constant horizontal or vertical velocity?

A

Constant horizontal, the vertical velocity increases

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13
Q

What is newton third law of motion?

A

He said every action has an equal reaction (mass x velocity = momentum)

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14
Q

What usually causes crash and sporting injuries?

A

Fast deceleration

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15
Q

How is momentum conserved in gun recoil?

A

The bullet is fired and moves faster than the run but the total momentum is zero because the run has a larger mass, therefore the have the same momentum in opposite directions and cancel each other out.

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16
Q

How is momentum conserved in explosions?

A

The momentum is zero because the momentum of one fragment flying out one way is cancelled by another flying in the other direction at the same momentum

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17
Q

How is momentum conserved in rocket propulsion?

A

The forward momentum of the rocket is cancelled out by the backward momentum of the gas that is fired out

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18
Q

How is energy conserved in a collision?

A

If two objects coalesce the momentum after must equal the total of their individual momentums

M1 u1 + m2 u2 = (m1 + m2) v

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19
Q

What is pressure?

A

When gas particles collide with the walls of their container and they exert force on the wall

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20
Q

How is pressure increased?

A

When there are greater numbers of collisions between the particles and the wall (more KE by heating)

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21
Q

How does the particle hitting the wall exert pressure? (Incl. equation)

A

The particle undergoes a change in its momentum and the size of the force depends on the length of time that the particle is in contact with the wall (time taken)

Change in momentum = force x time taken

22
Q

Where does the force that propels a rocket come from?

A

The exhaust gases - the force of the gas pushing out equals the forward force of the rocket, the particles of gas collide with the walls of the rocket which creates lots of force

Lots of particles are needed and they need to be moving fast so there a more collisions

23
Q

What frequency radio waves pass through earths atmosphere?

A

Between 30MHz and 30GHz

24
Q

What frequency radio waves are reduced or stopped by earth atmosphere?

A

Above 30GHz

25
Q

What frequency radio waves are reflected by earths atmosphere (the ionosphere)?

A

Below 30MHz

26
Q

What is diffraction?

A

When waves spread out around an obstacle or through a gap

27
Q

How can you increase diffraction?

A

By having the gap the same size as the wavelength

28
Q

How can you decrease diffraction?

A

By having a gap larger than the wavelength

29
Q

How can you stop diffraction?

A

By using a really big gap so the waves can pass straight through

30
Q

What do you need to get a stable interference pattern?

A

Two coherent sources - they both have the same frequency and amplitude, and are in phase

31
Q

What is path difference?

A

The difference in path of two waves - odd number of half wavelengths for destructive interference, even for constructive

32
Q

What type of waves can be plane polarised?

A

Transverse

33
Q

How does polarisation work?

A

Vertical polarisers only let vertically oscillating waves through and then the horizontal polariser only lets horizontally oscillating waves through so no light passes through

34
Q

How do polarising lenses work practically?

A

They absorb (partially polarise) light thats reflected off shiny surfaces and reduce glare

35
Q

What is evidence for light being a particle?

A

It reflects, travels in straight lines, doesn’t bend

36
Q

What is evidence for light being a wave?

A

It reflects, it diffracts and it creates interference and can be split into a spectrum amongst other experiments

37
Q

What is the normal?

A

A line 90° to the surface of a medium

38
Q

What is the angle of refraction?

A

The angle that light travels through a second medium

39
Q

What is the angle of incidence?

A

The angle that the light hits the boundary between the media

40
Q

What is refractive index?

A

A measure of how much the medium refracts light rays

41
Q

When does refraction increase and what does this mean about the critical angle?

A

When there’s a greater change in the light’s wave speed when in passes through the media.

Materials with higher refractive indices have a smaller critical angle

42
Q

What is the critical angle of diamond?

A

24.4

43
Q

What happens if the angle of incidence is less than the critical angle?

A

The wave is refracted (mostly)

44
Q

What happens if the wave hits the boundary at the critical angle?

A

It undergoes maximum diffraction and travels 90° to the normal (along the boundary)

45
Q

What happens if the angle of incidence is larger than the critical angle?

A

No light is refracted, all light is totally internally reflected

46
Q

What is dispersion?

A

When light travels through a prism and the different colours are refracted at different speeds because some (red) have longer wavelengths and some (blue/indigo/violet) have shorter wavelengths. Colours with shorter wavelengths are slowed down more and therefore deviate more

47
Q

How can you describe dispersion related to refractive indices?

A

Glass has a higher refractive index for the colours of shorter wavelength - blue light has a greater refractive index than red

48
Q

What are optical fibres used for?

A

To send digital signals for communication

In endoscopes to observe tissues inside the body

49
Q

What does a convex lens do?

A

It converges light rays at the focal point

50
Q

What is focal length?

A

The distance between the centre of the lens and the focal point

51
Q

What do you have to do the get light to refract more?

A

Use a fatter lens or move it further away from the screen

GCSE Physics OCR B (6 decks)

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