Measuring the speed of water waves from distance and time | Starter Quiz | Oak National Academy

Match the following quantities to their units.

• speed

• seconds (s)

• distance

• metres (m)

• time

• metres per second (m/s)

Answer explanation

In science, distance is measured in metres (m), time is measured in seconds (s) and speed is measured in metres per second (m/s).

Which of the following is the correct equation for speed?

• speed = distance x time

• speed = distance + time

• speed = distance – time

• speed = distance ÷ time

Answer explanation

Speed can be found using the equation: speed = distance ÷ time.

Which of the following is not a unit of speed?

• metres per second (m/s)

• metres per second squared (m/s²)

• kilometres per second (km/s)

• miles per hour (mph)

Answer explanation

In science, speed is measured in metres per second (m/s), but any unit that contains a distance unit (e.g. metres, miles) divided by a time unit (e.g. seconds, hours) is a unit for speed. Metres per second squared (m/s²) is the unit of acceleration.

Sam take three repeat measurements for the time taken for a wave to travel a set distance. The results are 0.21 s, 0.19 s and 0.26 s. Calculate the mean time. You do not need to include the units.

Answer explanation

The mean time is: 0.21 s + 0.19 s + 0.26 s = 0.66 0.66 / 3 = 0.22 s

What effect do random errors have on repeat readings?

• Random errors make repeat readings identical.

• Random errors make repeat readings slightly different to each other.

• Random errors make repeat readings more accurate.

• Random errors make all repeat readings inaccurate by the same amount.

Answer explanation

Random errors make repeat readings slightly different to each other. Calculating a mean value reduces the effect of random errors.

The uncertainty in a measured value refers to ...

• the accuracy of the result.

• the validity of the result.

• the amount of doubt about the result.

• the amount of certainty about the result

Answer explanation

The uncertainty in a measured value is the amount of doubt about the result which can arise from the accuracy or precision of the measuring instrument or errors made when taking the measurement or both.