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

Match the key word or phrase to the explanation.

• direct proportional

• when the same results can be achieved by a different person or method

• repeatable

• the speed at a particular moment in time

• instantaneous speed

• when the same results can be achieved by the same person and method

• reproducible

• when one variable is a constant multiple of the other

Answer explanation

An experiment is repeatable when the same results can be achieved by the same person and method, and reproducible if other people can get the same results. Variables are in direct proportion when one is a constant multiple of the other.

How can you check that a practical result is reproducible?

• Plot a graph to see if there is a relationship between variables.

• Collect another set of results to compare with the first.

• Have another person follow the same method and compare their results with yours.

• Compare you final answers with values from a textbook.

Answer explanation

The results are reproducible if other people follow the same method and get the same (or very similar) results to you.

Which of these should be included in a good written method?

• A clear set of instructions that will allow valid data to be collected.

• A description of how the control variables will be controlled.

• A complete set of results.

• A suitable range for the independent variable.

• A graph of the results.

Answer explanation

The method needs to be usable by someone else so should have a clear set of instructions, a description of how the control variables will be controlled and a suitable range for the independent variable (amongst other things).

A pupil produces a graph to see if there is a relationship between two variables. What features would the graph have if the variables are directly proportional to each other?

• The line of best fit is curved

• The line of best fit is straight.

• The gradient of the line is zero (flat).

• The line of best fit passes through the origin (0,0).

• The line of best fit is vertical (goes straight up).

Answer explanation

The graph would have a straight line of best fit that passes through the origin.

A pupil produces a graph to see if there is a relationship between two variables. The points do not seem to follow a straight line. How should they draw a line of best fit?

• Repeat the experiment until they get results that will give a straight line.

• Join the points with a series of straight lines, like a dot-to-dot.

• Draw a single straight line from the origin to the last point plotted.

• Draw a single curved line that passes through, or close to, the points.

• Draw a series of curves through the points.

Answer explanation

The pupil should draw a single curved line that passes through, or close to, the points.

A pupil suggests measuring the time it takes a trolley to roll 5 cm down a ramp using a stopwatch to get an accurate value of instantaneous speed. Why is this unlikely to produce an accurate result?

• The time is very short so would produce a very small error in the speed.

• The time is very short so would produce a very large error in the speed.

• It is hard to measure 5 cm accurately.

• It will not be possible to start and stop the watch accurately.

• The distance is too large to estimate instantaneous speed over.

Answer explanation

It would be very hard to measure a small amount of time accurately using a manual stopwatch. This error is more significant for small times and so will produce a larger error in speed calculations.