Measurement, units and uncertaintyIB MYP Physics: Subtopic test

1. 1
   A student in Nairobi is helping to set up a school sports day. She measures the length of the running track as 24 000 mm and the mass of the winner's trophy as 2.5 kg.

   (a)

   What is the length of the track in metres?

   [1 mark]

   • A2.4 m
   • B2400 m
   • C24 m
   • D24 000 000 m

   (b)

   What is the mass of the trophy in grams?

   [1 mark]

   • A0.0025 g
   • B25 g
   • C250 g
   • D2500 g

   (c)

   State the SI unit, with its symbol, for force and for pressure.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Amara and Luis each time 20 swings of the same pendulum with a stopwatch. A laser timer shows the true time is 28.4 s. Amara's four readings are 31.2 s, 31.3 s, 31.2 s and 31.3 s. Luis's four readings are 27.1 s, 29.8 s, 28.0 s and 29.6 s.

   (a)

   Which statement describes Amara's results?

   [1 mark]

   • AAccurate but not precise
   • BPrecise but not accurate
   • CBoth accurate and precise
   • DNeither accurate nor precise

   (b)

   Amara's readings are all too high by about the same amount. What is the most likely type of error?

   [1 mark]

   • AA systematic error, because every reading is shifted in the same direction
   • BA random error, because the readings are not exactly the same
   • CNo error, because the readings agree closely
   • DA random error that more repeats and a mean would remove

   (c)

   Calculate the mean of Luis's four readings. Give your answer to one decimal place.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A class in Lisbon investigates how far a spring stretches when masses are hung from it. They hang masses from 100 g to 500 g, one at a time, and measure the length of the spring with a 30 cm ruler marked in millimetres. They will plot a graph of their results.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Outline how the students should record and process their results so that random errors are reduced and the relationship between mass and extension can be seen.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school athletics club in Singapore times its 100 m sprinters with handheld stopwatches. A student suggests buying electronic timing gates, which cost much more. As a test, the club times one runner five times with a stopwatch and records 13.4 s, 13.6 s, 13.5 s, 14.3 s and 13.5 s.

   (a)

   Process the club's data. Identify the anomalous result and suggest a cause. Then calculate the mean time without it, and use the range of the remaining readings to comment on how precise they are.

   [6 marks]

   (b)

   Discuss whether the club should buy electronic timing gates instead of using stopwatches.

   [6 marks]

   Total for question 4: 12 marks

End of questions