Yr 8 Revision - energy and waves

Yr 8 Revision - energy and waves

Work done formula

• work done (Joules) = force (Newtons) ´ distance (metres)

Multiple Select

Calculate the work done by a force of 1.4N when it moves an object by 4m. Choose the correct answer(s) from the options given.

• 5.6 J

• 56 J

• 5.6 Nm

• 0.56 J

Multiple Choice

What is the distance moved by a force 8 N when it does work of 90J on an object

• 0.089 m

• 11.25 m

• 720 m

• 0.090 m

Multiple Choice

What force is required to move 7 m if the work done is 9 J?

• 0.77 N

• 0.78 N

• 63 N

• 1.285 N

Features of waves

• Wavelength – The distance between a crest and a trough or a compression and a rarefaction

• Frequency- The number of vibrations in a second

• Longitudinal wave - The particles in the medium vibrate to and fro in a direction parallel to the movement of the wave.

• Transverse wave - The particles in the medium vibrate up and down in a direction perpendicular to the movement of the wave.

Multiple Select

Choose the correct answer(s).

Frequency is

• number of vibrations in one second

• number of oscillations in one second

• the height of a wave

• The length of one wave

Multiple Choice

Amplitude is

• the length of a wave

• the height of a wave

• the number of waves

• the maximum height of a peak

Multiple Choice

Wavelength is

• the maximum height of a peak

• the maximum length of a wave

• the length of a crest or trough

• the distance between two consecutive crests

Sound waves

• compression - particles are closer together- high pressure

• rarefaction - particles are far apart-low pressure

• longitudinal wave

Travel of sound waves

• loud speaker vibrates

• particles close to the loud speaker vibrate

• the neighbouring particles vibrate

• the vibrations hit the ear drum

• the sound is heard

Speed of sound waves

• The closer the particles the more the speed of the sound

• 
  

• 
  

• 
  

Fill in the Blanks

Sound needs a

to travel

Fill in the Blanks

Sound cannot travel in -------------------

Fill in the Blanks

The sound waves are produced due to the ---------------------- of the particles of the medium

Fill in the Blanks

The speed of sound is -------------------- in solids compared to liquids

Multiple Select

Choose the correct answer (s)

Human hearing frequency

• 50 Hz

• 50 kHz

• 20 kHz

• 15 Hz

Multiple Choice

Infra sound frequency

• 10 Hz

• 100 Hz

• 10 kHz

• 1000 Hz

Multiple Select

Choose the correct answer(s)

Ultrasound frequency

• 25 Hz

• 25 kHz

• 2500 Hz

• 250 kHz

EM Spectrum order

• frequency of the waves increase as we go down the spectrum

• Wavelength of the waves decrease as we go down the spectrum.

• Waves having longer wavelength can cause heating of the body cells

• Waves having shorter wavelength can cause ionisation of the body cells.

Multiple Select

Choose the correct answer(s)

The waves are arranged in the order of

• increasing frequency

• increasing energy

• increasing wavelength

• increasing amplitude

Multiple Choice

Which of the following order of waves is correct

• Radio waves, visible, ultra violet, x rays, gamma rays, microwaves, infrared

• Radio waves, x rays, gamma rays, microwaves, infrared, visible, ultra violet

• Radio waves, infrared, microwaves, ultra violet, visible, x rays, gamma rays

• Radio waves, microwaves, infrared, visible, ultra violet, x rays, gamma rays

Poll

Radio waves can cause ionisation

• yes

• no

• maybe

Poll

Gamma rays can cause ionisation

• yes

• no

• maybe

Superposition of waves

• Waves add up or cancel

• when waves are in step with each other, they add up and we get a combined wave

• when waves are out of step with each other, they cancel out and we get no wave

Multiple Choice

When waves add up their

• energy increases

• wavelength increases

• amplitude increases

• frequency increases

Multiple Select

Choose the correct answer(s)

When waves that are out of step superpose

• energy becomes zero

• wavelength becomes zero

• frequency becomes zero

• amplitude becomes zero