Physics yr9

• Sound travels through solids, liquids or gases
• Speed of sound = frequency x wavelength
• The speed of sound is the distance travelled by sound per second
• In air at room temperature, the speed of sound is approximately 340 m/s
• Reflection occurs when sound waves bounce off an object
• When an object vibrates it produces waves that travel outwards from its surface
• Waves are disturbances that transfer energy without moving matter
• When sound waves travel from one medium to another, they change direction because their speeds are different.
• A wave can be described as a disturbance which transfers energy without transferring matter
• Echoes are caused by reflection
• When an object vibrates it creates waves that travel outwards from its surface
• When sound reflects from a smooth surface it will be reflected back with little change to its direction
• Waves are made up of oscillations (vibrating particles)
• A wavefront is a line on which all points have the same phase (the same displacement)
• Sound travels faster through solids than liquids or gases
• A wavefront is the boundary between two regions with different amplitudes of a wave
• Sound travels faster through solids than liquids or gases
• An amplitude is the maximum displacement of a particle from its equilibrium position
• The wavelength of a wave is the distance between two consecutive crests or troughs
• The wavelength is the distance between two consecutive points on a wave that have the same phase
• Speed = Distance / Time
• The amplitude is the maximum displacement of a particle from its equilibrium position
• The speed of sound is the distance travelled divided by time taken
• If two objects produce sounds at the same time but have slightly different frequencies then we hear them separately
• The speed of sound is determined by the temperature of the air
• Frequency is how many times something happens per second
• The speed of a wave is the distance travelled divided by time taken
• Infrasound has frequencies below 20Hz
• The speed of a wave depends on the medium it's travelling through, the frequency of the wave and the wavelength of the wave
• If the amplitude of a wave increases then so does the intensity
• Intensity = power per unit area
• Waves can be reflected, refracted, diffracted and absorbed by materials they encounter
• The wavelength is the distance between two consecutive crests, troughs, or any other point on a wave
• The wavelength is the distance between two consecutive crests, troughs, nodes or antinodes.
• Frequency is the number of waves that pass a given point per second
• When light waves are reflected off a surface, some of them bounce back into space while others enter your eye
• Period is the time taken to complete one cycle of a wave
• Period is the time taken to complete one cycle
• Light waves that hit an object at an angle will reflect off it at the same angle
• A car speeds up for 20 seconds increasing in speed from 10 m/s to 30 m/s - what is the acceleration?

  Change in velocity = 30 - 10 = 20 m/s 20/20 = 1m/s