Measuring instantaneous speed practical (v=s/t) | Exit Quiz | Oak National Academy

Match the key words or phrases to their definitions.

• anomalous reading

• a wheeled object used in motion experiments

• dynamics trolley

• the speed of an object at a particular moment

• instantaneous speed

• a result which does not fit the pattern of a set of results

• average speed

• the total distance travelled divided by the time taken

Answer explanation

The total distance travelled every second is the average speed whilst the speed at a particular moment is instantaneous speed. A dynamics trolley is a wheeled object used in experiments. Anomalous readings do not fit the pattern of the other results.

Which of these statements about instantaneous and average speed is correct?

• The instantaneous speed of an object is always less than the average speed.

• The instantaneous speed of an object is always greater than the average speed.

• The instantaneous speed of an object is always the same as the average speed.

• The instantaneous speed of an object can change during a journey.

• The instantaneous speed of an object is constant during a journey.

Answer explanation

The instantaneous speed of an object changes during most journeys; at times it will be travelling faster than it is at other times.

A student investigates the relationship between the steepness of a ramp and the instantaneous speed of a trolley at the end of the ramp. Which of these are control variables for the investigation?

• The speed of the trolley at the end of the ramp.

• The steepness of the ramp.

• The length of the ramp.

• The distance the speed is measured over.

• The mass of the trolley.

Answer explanation

The steepness of the ramp is the independent variable and the speed of the trolley is the dependent variable. All of the other variables are control variables.

A trolley rolls down a ramp and passes between two markers that are 20 cm apart in a time of 0.25 s. Calculate the speed of the trolley in m/s.

Answer explanation

20 cm = 0.2 m so v = s ÷ t = 0.20 m ÷ 0.25 s = 0.8 m/s

A pupil collects the following set of timing data for a moving object: 0.25 s, 0.23 s, 0.35 s, 0.22 s, 0.21 s. Which calculation should the pupil use to find the mean time?

• mean time = (0.25 + 0.23 + 0.35 + 0.22 + 0.21) ÷ 5

• mean time = (0.25 + 0.23 + 0.22 + 0.21) ÷ 5

• mean time = (0.25 + 0.23 + 0.35 + 0.22 + 0.21) ÷ 4

• mean time = (0.25 + 0.23 + 0.35 + 0.22) ÷ 4

• mean time = (0.25 + 0.23 + 0.22 + 0.21) ÷ 4

Answer explanation

0.35 s is an anomalous result so should not be used. This leaves 4 values to find the mean for so the calculation that should be used is: mean time = (0.25 + 0.23 + 0.22 + 0.21) ÷ 4

A trolley rolls down a ramp passing between two markers, 0.20 m apart. The following results are collected: 0.17 s, 0.18 s, 0.17 s, and 0.20 s. Calculate the mean instantaneous speed for the trolley.

• 0.18 m/s

• 1.1 m/s

• 1.0 m/s

• 0.35 m/s

• 0.28 m/s

Answer explanation

mean time = (0.17 + 0.18 + 0.17 + 0.20) ÷ 4 = 0.18 s v = s ÷ t = 0.20 m ÷ 0.18 s = 1.1 m/s