Quick answer: SI units are the internationally agreed units for measurement: metre for length, kilogram for mass, second for time, ampere for current and kelvin for temperature. This Physics 9-10 worksheet on SI units gives 20 problems from easy to hard: base units, prefix factors and simple conversions. The worked answers are on a separate page, and the worksheet is a free printable PDF.
Also, these problems train you to handle units and numbers like a scientist. In addition, you will convert between prefixes, use standard form, count and round significant figures, read an instrument and judge how reliable a set of readings is.
They suit GCSE and IGCSE students, O Level and Class 9-10 learners, and they start with recall before moving to multi-step work and error spotting.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: GCSE WS, IGCSE 1.1
Problem 1 Base units ★★★
Aarav in Pune lists the quantities length, mass, time, electric current and temperature.1. Also, name the SI base unit for each quantity.
2. Then give the symbol of each unit.
3. Finally, state which base unit already contains a prefix.
Problem 2 Prefix factors ★★★
Moreover, write each prefix as a power of ten.1. kilo
2. milli
3. micro
4. giga
Problem 3 Simple conversions ★★★
Convert.1. 2.5 km to metres
2. 340 mm to metres
3. 75 cm to metres
4. 0.8 kg to grams
Problem 4 Standard form ★★★
1. Write 45 000 000 in standard form.2. Then write 0.00062 in standard form.
3. Next, write 3.8 × 10³ as an ordinary number.
4. Finally, write 7.1 × 10⁻² as an ordinary number.
Problem 5 Counting significant figures ★★★
Also, state the number of significant figures in each value.1. 502
2. 0.0405
3. 1.050
4. 0.0090
Problem 6 Rounding ★★★
Round each value to the number of significant figures in brackets.1. 3.14159 (3)
2. 0.0067892 (2)
3. 25 481 (2)
4. 9.996 (3)
Problem 7 Reading a ruler ★★★
Chiamaka in Lagos measures a strip of card with the ruler shown.1. In addition, state the resolution of the ruler.
2. Then record the length of the strip.
3. Finally, give the reading in metres.
Problem 8 Area of a tile ★★★
Aarav measures a tile as 18.4 cm by 12.5 cm.1. Calculate the area in cm².
2. Then give the area in m².
3. Finally, state the number of significant figures in each measurement.
Problem 9 Area and volume units ★★★
1. Convert 3.2 m² to cm².2. Then convert 450 cm³ to m³ in standard form.
3. Finally, explain why 1 m² is not 100 cm².
Problem 10 Time conversions ★★★
Convert each time to seconds.1. 2.4 hours
2. 45 minutes 30 seconds
3. 0.5 milliseconds (standard form)
Problem 11 Averaging a pendulum ★★★
Kofi in Accra times 10 swings of a pendulum five times: 14.8 s, 15.2 s, 15.0 s, 14.9 s, 15.1 s.1. Calculate the mean time for 10 swings.
2. Then calculate the time for one swing.
3. Finally, state the uncertainty in the mean, using half the range.
Problem 12 Two balances ★★★
Mei in Singapore checks balances with a standard mass of true value 5.00 g. Balance A reads 5.31 g, 5.30 g, 5.32 g. Balance B reads 4.9 g, 5.2 g, 5.0 g, 4.9 g.1. Also, calculate the mean for each balance.
2. Then state which balance is more precise.
3. Finally, state which balance is more accurate.
Problem 13 Percentage uncertainty ★★★
1. A length is recorded as 25.0 cm ± 0.5 cm. Calculate the percentage uncertainty.2. A time is recorded as 0.40 s ± 0.01 s. Calculate the percentage uncertainty.
3. Finally, state which measurement has the smaller percentage uncertainty.
Problem 14 Density from a block ★★★
Bilal in Lahore has a metal block of mass 540 g with the edges shown.1. Calculate its volume in cm³.
2. Then calculate its density in g/cm³.
3. Finally, convert the density to kg/m³.
Problem 15 Thickness of a sheet ★★★
Diego in Texas measures a stack of 200 sheets of paper as 2.0 cm ± 0.1 cm thick.1. Moreover, calculate the thickness of one sheet in mm.
2. Then calculate the percentage uncertainty of the stack.
3. Next, state the thickness of one sheet with its uncertainty in mm.
4. Finally, write the thickness in metres in standard form.
Problem 16 Speed and sensible rounding ★★★
In addition, a sprinter in Nairobi covers 100.0 m in 12.4 s.1. Also, calculate the average speed with a calculator.
2. Then give it to a sensible number of significant figures.
3. Finally, explain your choice.
Problem 17 Speed unit change ★★★
1. Convert 90 km/h to m/s.2. Then convert 1.2 × 10⁻³ m³ to litres, given 1 m³ = 1000 L.
3. Finally, convert 20 m/s to km/h.
Problem 18 Distance light travels in a year ★★★
Light travels at 3.0 × 10⁸ m/s. A year contains about 3.2 × 10⁷ s.1. Calculate the distance light travels in a year, in standard form.
2. Then convert your answer to kilometres.
3. Finally, state the number of significant figures you used.
Problem 19 Spot the errors ★★★
A student writes: “5.6 mm = 5600 m” and “0.75 µA = 7.5 × 10⁻³ A”.1. Explain the error in the first statement and correct it.
2. Then explain the error in the second statement and correct it.
3. Finally, convert 0.75 µA to milliamperes.
Problem 20 Which result to trust ★★★
Three groups measure the length of a corridor whose true length is 12.40 m. Group 1: 12.41 m, 12.40 m, 12.42 m. Then group 2: 12.78 m, 12.80 m, 12.79 m. Group 3: 12.1 m, 12.7 m, 12.4 m.1. Calculate the mean for each group.
2. Then compare the precision of the groups.
3. Next, compare the accuracy of the three means.
4. Finally, suggest a cause of the error in Group 2.
