paper 2

• Why does the speed of a runner change during a race? (4 marks)

  Start - accelerate and speed increases

  Middle - road is not flat - speed decreases (uphill - force of gravity pushes down) speed increases (down hill - force of gravity)

  Resistive forces (air) increases/decrease - acceleration/deceleration

  End - tire and less force exerted - speed deceases
• Why does an objects velocity decrease after a collision (momentum?

  Momentum is conserved in the collision

  Momentum of carriage increases

  Momentum of train decreases (Newton's thirds law)

  momentum = mass x velocity - mass = constant and velocity decreases, therefore momentum decreases
• LOOK AT DIAGRAM IN ORDER TO IDENTIFY THE PROBLEM IN EXPERIMENTS
• Why does temperature remain constant?

  Flasks absorb infrared radiation and transfer it to the surroundings

  At first, the rate of absorption of infrared radiation is greater than the rate of energy transfer to the surroundings

  The rate of energy transfer increases as the temperature of the flask increases

  The rate of energy transfer to the surroundings = the rate of energy transfer to the flask
• Velocity time graphs - area under graph = distance travelled
• Velocity time graphs - gradient = acceleration
• What happens when a car brakes?

  Force applied to brakes - work done by friction between brakes and tyre

  reduces Ek of vehicle - slows down and cause brake temperature to increase

  faster travels - greater braking force needed

  greater braking force - greater deceleration

  leads to brakes overheating and driver loses control of vehicle
• speed double - thinking distance doubles and braking distance x 4
• Radio waves ?

  Aerial absorbs radio waves

  Electrons are made to vibrate

  Creates an alternating current that is the same frequency as the radio wave
• gamma rays?

  changes in atoms and nuclei can result in electromagnetic waves being generated/absorbed over a wide frequency range

  originate from changes to the nucleus of an atom