Physics

• Momentum is how hard it is to stop an object from moving
• Factors affecting momentum:

  Velocity

  Mass
• Inertia is the tendency for an object to keep moving or staying still
• All moving objects have momentum
• Momentum is a vector
• In a closed system, total momentum of 2 objects before and after an event is equal
• When a moving object hits a stationary object in a closed system, the moving object loses momentum and the stationary object gains momentum
• Resultant forces can be broken down into their vertical and horizontal forces
• When resultant force is 0, an object is moving at a constant speed
• If a resultant force isn't 0, the object is accelerating, decelerating or changing directions
• Transverse waves oscillate perpendicular to energy transferred.
• Wavespeed = frequency × wavelength
• Colliding waves can get:

  Absorbed

  Reflected

  Transmitted
• Reflection = light bouncing off a surface
• Law of reflection: angle of incidence = angle of refraction
• When a wave changes medium e.g. air and water, speed and direction changes
• Soundwaves are longitudinal
• Human hearing range = 20 - 20,000 Hz
• Pinna - visible ear

  Ear Canal - middle of ear

  Ear Drum - end of canal
• Ultrasound = +20,000 Hz
• Ultrasound is partially reflected when hitting a surface
• Distance wave travels = speed of sound in body × time taken
• Sonar detects ultrasound reflection
• Wave period = time for wave to pass 1 point
• Richer scale is logarithmic
• Earth layers:

  Solid crust

  Plasticy mantle

  Liquid outer core

  Solid inner core
• Magma is liquid rock
• Longitudinal waves oscillate parallel to energy transferred
• Mantle is moldable rock and some pockets of magma
• P waves are longitudinal
• S waves are transverse
• P waved and S waves refract under the mantle
• S waves can't travel through liquid and so the outer core
• The mantle and outer core has different densities so P waves refract
• Humans can see 350 NM to 650 NM
• 1 NM= 1 m × 10 ^ 9
• EM waves are transverse
• Transverse waves don't need a medium to travel
• Change in Energy = Mass × SHC × Change in Temperature
• Good emitters of heat are good absorbers of heat