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Recap Year 9: Physics

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  • State Newton’s Second Law of Motion.
    The force on an object is equal to the rate of change of momentum / F = ma.
  • A force of 30 N acts on a 6 kg object. Find acceleration.
    a = F ÷ m = 30 ÷ 6 = 5 m/s²
  • Which of the following is a scalar quantity: velocity, force, distance, displacement?
    distance
  • Define speed.
    Distance travelled per unit time.
  • A student measures a time interval of 2.5 minutes. Express this in seconds.
    150 s
  • State the difference between speed and velocity.
    Speed is scalar (no direction), velocity is vector (includes direction).
  • Differentiate between mass and weight.
    Mass is the amount of matter in an object (kg, scalar), weight is the force of gravity on the object (N, vector).
  • Convert your answer in Q7 to SI unit (kg/m³).
    4000 kg/m³
  • Define vector quantity. Give one example.
    A physical quantity that has both magnitude and direction, e.g. velocity / displacement / force
  • State the SI unit of mass.
    kilogram (kg)
  • From a velocity-time graph, what does the slope represent?
    Acceleration
  • A block has mass 200 g and volume 50 cm³. Find its density in g/cm³.
    200 ÷ 50 = 4 g/cm³
  • A car travels 100 m in 20 s. Calculate its average speed.
    100 ÷ 20 = 5 m/s
  • How do you determine the volume of an irregular solid object?
    Use displacement method (measure volume of water displaced in measuring cylinder).
  • A ball increases its velocity from 4 m/s to 10 m/s in 3 s. Find acceleration.
    (10 – 4) ÷ 3 = 2 m/s²
  • From a velocity-time graph, what does the area under the graph represent?
    Displacement
  • State the formula for density.
    density = mass ÷ volume
  • Why does a wooden block float on water while a metal block sinks?
    Because density of wood < density of water, while density of metal > density of water.
  • Name one instrument used to measure length accurately.
    Vernier caliper / micrometer screw gauge
  • Define acceleration.
    Rate of change of velocity per unit time.