Physics paper 1

• What do horizontal sections on a velocity-time graph tell you about the motion of the object ?

  The object is moving with a constant velocity
• How is increasing deceleration shown on a velocity-time graph ?

  A downward curve with an increasingly steep gradient
• According to the laws of motion, what is needed to make an object accelerate ?

  An unbalanced/resultant force acting on the object
• If the resultant force acting on a lorry driving down a road is zero, what do you know about its velocity ?

  It remains the same/is constant
• Give the equation for the relationship between force, mass and acceleration

  Force = mass x acceleration (F = m x a)
• What‘s the formula used to calculate momentum ?

  Momentum = mass x velocity (p = m x v)
• True or false ? Momentum of a system is conserved when no external forces act

  True
• The momentum of a seed pod before it explodes is zero. Explain how the total momentum after the explosion can still be zero even though pieces fly off

  In an explosion, although the individual pieces have momentum, they fly off in different directions, so their total momentum can cancel out to zero
• What happens to a moving objects momentum when a non-zero resultant force acts on that object ?

  The force causes a change in the object’s momentum
• What is the amplitude of a wave ?

  The height of the wave from the rest position to the top or bottom of a peak
• What is the wavelength of a wave ?

  The horizontal distance from one peak to the next
• What is meant by the period of a wave ?

  The time it takes for one complete wave to pass a point
• True or false ? Both transverse and longitudinal waves have compressions

  False
• What does a wave not transfer ?

  Matter
• What does the refractive index of a transparent material tell you ?

  It tells you how fast light travels through the material/the ratio of the speed of the light in a vacuum to the speed of light in the material
• True or false ? The critical angle of refraction = 90 degrees

  True
• What is the relationship between the critical angle and refractive index ?

  Sin C = 1/n
• True or false ? Sound waves are transverse waves

  False
• True or false ? Sound waves can be reflected but not refracted

  False
• What is the lowest frequency of sound that a human can normally hear ?

  20 Hz
• True or false ? The frequency, amplitude and period of a sound wave can all be measured using a microphone and an oscilloscope

  True
• Why can’t you measure the speed of a wave from an oscilloscope trace alone ?

  The oscilloscope trace doesn’t give wavelength
• True or false ? An alpha particle is the same as a hydrogen nucleus

  False
• Give one way that radioactivity can be measured or detected

  Using a Geiger-Müller detector or photographic film
• What are gamma rays ?

  Short wavelength electromagnetic radiation emitted by the nucleus of an atom
• What is a beta particle ?

  An electron
• Define half-life in terms of the decay of radioactive atoms in a sample

  The half life is the time taken for half of the radioactive atoms now present to decay
• True or false ? All radioactive isotopes have the same half-life

  False
• True or false ? Half-life is the time taken for the count rate of a sample to halve

  True
• How many half-lives would it take for the number of nuclei of a radioactive isotope to decrease to 1/8 of its initial value ?

  3 half-lives
• Why is radiation used to sterilise food ?

  Radiation kills cells, so it can kill all the microbes on and in the food
• Name one other thing that is sterilised by radiation

  Medical equipment
• How long should the half-life of a source used for sterilisation be ? Why ?

  The source should have a reasonably long half-life. For example, this means that it won’t need to be replaced too often
• True or false ? Irradiation of an object causes it to become radioactive

  False
• Give four ways that the risk of irradiation by a source can be reduced

  For example, by keeping the source in a lead-lined box, standing behind barriers, leaving the room, using remote controlled arms
• Give two way that the risk of contamination of a source can be reduced

  For example, gloves and tongs can be used when handling the source, protective suits and masks can be worn to prevent the breathing in of particles
• Why is shielding used around a nuclear fission reactor ?

  To absorb the highly-penetrating ionising radiation that is released in the fission reactions
• In a nuclear fission reactor, what is the moderator for ?

  It slows down fast-moving neutrons, so they can be absorbed by uranium nuclei
• What do control rods do in a nuclear fission reactor ?

  They limit the rate of fission by absorbing excess neutrons
• What is meant by nuclear fusion ?

  Where two light nuclei collide and join to create a larger, heavier nucleus