1. 1
   A physics technician uses a micrometer screw gauge to measure the diameter of a copper wire. The instrument display reads 0.45 millimetres. The technician also records the length of the wire as 1.2 metres and its mass as 850 milligrams.

   (a)

   What is the SI base unit for length?

   [1 mark]

   • AInch
   • BCentimetre
   • CMetre
   • DFoot

   (b)

   Which of the following is the correct value of the wire's diameter in metres, given the micrometer reading of 0.45 millimetres?

   [1 mark]

   • A4.5 x 10^-1 m
   • B4.5 x 10^-2 m
   • C4.5 x 10^2 m
   • D4.5 x 10^-4 m

   (c)

   Express the wire's mass of 850 milligrams in kilograms, giving your answer in standard form.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A long-distance runner completes a marathon course. Her coach records that she took 3.5 hours to finish, and the coach wants to express her average speed for the race in the SI unit of speed, metres per second.

   (a)

   What is the SI unit for time?

   [1 mark]

   • ASecond
   • BMinute
   • CHour
   • DDay

   (b)

   Which prefix, when attached to a unit, represents a multiplying factor of x1000 (10^3)?

   [1 mark]

   • ACenti
   • BMilli
   • CKilo
   • DMicro

   (c)

   Calculate the number of seconds in the 3.5 hours the runner took to complete the marathon.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A research scientist is studying the growth of bacteria under a microscope. A single bacterial cell is measured to have a width of 2500 nanometres. The scientist also records that the cell divides once every 1 800 000 microseconds.

   (a)

   Convert the width of the bacterial cell, 2500 nanometres, into metres, giving your answer in standard form to 2 significant figures.

   [3 marks]

   (b)

   The scientist records that the bacterial cell divides once every 1 800 000 microseconds. Convert this time into seconds, then into minutes, showing your working and giving your final answer to an appropriate number of significant figures.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A team of engineers is designing instruments for an international space mission. The mission requires precise measurement of quantities ranging from the enormous, such as distances between planets measured in billions of metres, to the extremely small, such as the diameter of dust particles measured in millionths of a metre. All partner nations in the mission must agree on how these quantities are measured, expressed and communicated.

   (a)

   Explain why the use of SI units, standard form and an agreed set of unit prefixes (such as giga, mega, kilo, centi, milli, micro and nano) is essential for the success of an international space mission such as this.

   [6 marks]

   (b)

   The engineers must combine a measurement of 3.2 gigametres (the distance to a target asteroid) with a measurement of 450 micrometres (the diameter of dust particles collected). Explain, using appropriate physics, the steps the engineers should take to convert both quantities into the same SI base unit, the number of significant figures they should quote in their final combined report, and why care with units and significant figures matters in this context.

   [6 marks]

   Total for question 4: 12 marks

End of questions