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Flashcards in Topic 3 Deck (47):
1

What’s gravitational potential energy

By a body due to its height above the Earth

Depends on the mass of the body
The gravitational field strength
The height the body is raised

2

Gpe equation

Mass x gravitational field strength x change in height


Change in gpe = m x g x change in H

3

What’s kinetic energy

Stored in moving objects

4

How do you work out ke

1/2 x m x speed^2

5

What’s KE proportional to

Directly proportional to the mass of the moving object

Doubling the mass doubles the KE of moving object


Directly proportional to the square of the speed so doubling the speed means the KE increases by a factor of four

6

What do waves do?

Transfer energy and information without transferring matter


Evidence for this is water wave can be seen when a ball dropped into a pond bobs up and down but the wave energy travels outwards as ripples across the surface of the pond

7

What can waves be described by?

Frequency

Speed

Wavelength

Amplitude

Period

8

Examples of longitudinal waves

Sound waves and seismic P waves

9

How do particles move in longitudinal waves

In the material the sound is travelling through move back and forth along the same direction that the sound is travelling

10

Which way do they move in longitudinal waves

Move along the same direction of the wave

11

Examples of transverse waves

Waves on a water surface

Electromagnetic

Seismic S

12

How do the particles move in transverse waves

Move in a direction at right angles to the direction the wave is travelling

Move across the direction the wave is travelling

13

Both equations for speed

Speed = d/t

Speed = frequency x wavelength

14

What are the names of the two methods of calculating the speed of sound in air

Using an echo


Using two microphones and an oscilloscope

15

How do you use an echo

Measure distance from sound and reflecting surface (wall)

Measure time interval between sound and echo

Use speed = distance/time

16

How do you use a microphone and an oscilloscope

Set up microphone one in front of the other at different distances in a straight line from a loudspeaker

Set the frequency of the sound from the loudspeaker to a known audible value

Display the two waveforms on the oscilloscope measure the distance between the microphones

Move the microphones apart so that the wave forms move apart by 1 wavelength

Wavespeed = frequency x wavelength

17

What do u need to work out the speed of ripples on the surface of water

A ripple tank and a strobe

18

How do u use a ripple tank

Set power supply to vibrate the paddle at a known frequency the image of waves are on screen use a strobe light to freeze the water waves so that you can measure the wavelength

19

When a sound/light/water wave reaches the boundary between two materials it can be :

Reflected
Refracted
Transmitted
Absorbed

20

The amount of reflection that happens at a boundary depends on

The densities of the materials

Greater the differences in density the more sound energy will be reflected

21

When is sound transmitted through a material

Similar densities

22

When is sound absorbed by materials

Depends on the material and the wavelength of sound - amount of absorption

23

When is sound reflected

Big difference in densities of the materials at an interface for example between air and concrete

24

What can refraction result in

Change of both speed and direction

25

When does the direction not change in refraction

When the wavefront is perpendicular to the normal

26

When do sound waves travel slower

In cooler denser air

27

When do water waves travel faster

In deep water

28

What’s refraction in its special case

When light sound or water waves move from one material into another their direction does not change if they are moving along the normal

29

What’s the process used by the ear to detect sound

Waves producing vibrations in solids

30

Vibration and waves

When objects vibrate
Sound waves produces
Sound waves are a series of oscillations that transfer energy from the source to the ear

31

What range can human ear detect frequencies

20Hz-20kHz

32

Energy transfer is

When air molecules are forced to vibrate by the source of the vibration energy travels via a longitudinal wave until it reaches the ear

33

How does the ear detect sound

Sound waves are channeled down the ear canal and cause the eardrum to vibrate

These vibrations pass through the ear as further vibrations are then converted to N electrical signal and carried to the brain

34

Why can humans only hear sound in the range 20Hz to20kHz

Sound waves are travelling from air into a solid ate converted to vibrations and travel through the solid as a series of vibrations this conversion of sound waves to vibrations in solids only works over a limited frequency range

35

What’s ultrasound

Sound waves with a frequency above 20kHz

36

What’s infrasound

Sound waves with a frequency lower than 20Hz

37

Exploring the earths core

Infrasound is believed to travel through the earth as shockwaves from tsunami volcanoes or earthquakes


Infrasound is also produced when meteors enter the earths atmosphere

Scientists can detect this infrasound and track the path the meteor will take


Infrasound waves can be detected from explosions under the ground. The infrasound waves can also help to determine the structure of rocks beneath the earths crust

38

Pre-natal scans

Ultrasound waves make inside body images

Not harmful

Safe on foetuses

Ultrasound waves sent into woman’s body and some of sound is reflected each time it meets a layer of tissue with a different density to the one it has just passed through.

Scanner detects echoes and a computer used information to make a picture

39

Sonar

Sonar uses impulses of ultrasound to find the depth of water beneath a ship the sonar equipment measure the time between sending the sound and detecting its echo

40

What happens when a sound wave moves from one material to another

The wave speed or velocity may change

Wavelength may change

Frequency will not change


Wave speed = frequency x wavelength

41

Wavelength is directly proportional to

Wave speed

42

Density and speed of sound and n steel

7.86

5940

43

Density and speed of sound in water

1

1496

44

Densityband speed of sound in fat

0.94 and 1450

45

Density and speed of sound in muscle

1.06 and 1580

46

Density and speed of sound in air

0.00139

331

47

Speed of sound info

Speed of sound in a material usually depends on the density of the material

More dense more speed since wave can be passed more easily from particle to particle