Speed and Sound Vocabulary
8.1 Speed
Speed is defined as the distance travelled per unit time:
SI unit of speed is metres per second (m/s).
Instantaneous speed is the speed at a particular instant.
Average speed is the total distance travelled divided by the total time taken:
8.2 Distance/Time Graphs
Distance/time graphs represent motion, with distance on the y-axis and time on the x-axis.
A straight line sloping upwards indicates constant speed.
A horizontal line indicates the object is stationary.
A non-straight line indicates changing speed.
9.1 Hearing Sound
Sound is a form of energy produced by vibrations.
Sound travels through a medium as waves, consisting of rarefactions and compressions.
Sound requires a medium (solid, liquid, or gas) to travel and cannot travel through a vacuum.
The ear detects sound by converting sound waves into electrical signals sent to the brain.
9.2 Pitch and Frequency
Pitch is related to frequency, which is the number of vibrations per second, measured in hertz (Hz).
High-pitched sounds have high frequencies, and low-pitched sounds have low frequencies.
Humans can hear sounds in the range of 20 Hz to 20,000 Hz.
Short, thin, and taut strings produce higher-pitched sounds.
9.3 Loudness and Amplitude
Loudness is related to the amplitude of a sound wave.
Large vibrations produce loud sounds with large amplitudes, while small vibrations produce soft sounds with small amplitudes.
Loud sounds carry more energy and can damage hearing.
Noise is unwanted or loud sound.
9.4 Tracing Sound Waves
An oscilloscope displays sound waves.
Amplitude is the extent to which air particles are displaced, seen as the height of the wave on the oscilloscope.
Frequency is the number of waves passing a point per second; high-pitched sounds have higher frequencies.
Loud sounds have larger amplitudes than soft sounds.