Explain why it is appropriate to repeat the measurements.
- (Repeating the measurement) reduces (the effect of) random error
(Caused by) variations in the temperature of the rubber bands
If its two marks include:
- (Repeat readings) allow a mean to be calculated to give a (more) accurate value
Criticise the recording of the data
- The values (of x and ) are not recorded to consistent decimal places
- There is no evidence of repeats
- There are not enough sets of data (to draw a reliable graph)
- The reading of x at 20.5 does not follow the trend
The student wrote a laboratory report about her investigation.
She reported that the most significant source of error was being unable to judge the
exact point where the ball landed. This was because the ball moved too quickly.
Explain one modification she could make to the apparatus to reduce this error.
You should include additional apparatus.
- Use a camera to record the motion
Which can be viewed in slow motion (to find the exact point where the ball
landed)
OR
- Place a tray of sand on the bench for the ball to land in
So that the ball remains stationary when it lands
Or so the ball leaves an indentation where it lands
To see for time if you don’t use a stop watch you could use a video cam or light gate:
- Use video camera
- Valid method to find time (e.g., count the number of frames)
- Place a light gate (at each marker)
To (start and) stop an electronic/digital timer
Or use a data logger/computer to determine the time
The student added water to the transparent tube to change the length s of the
air column.
Describe a method to determine a single value of s as accurately as possible, using a
metre rule.
- Clamp the metre rule in position
- Check the zero of the metre rule is level with the bottom of the transducer
- View (the metre rule) perpendicularly
- Ensure the metre rule is vertical using a set square
- (Repeating the measurement) reduces (the effect of) random error
(Caused by) variations in the temperature of the rubber bands
If its two marks include:
- (Repeat readings) allow a mean to be calculated to give a (more) accurate value
Criticise the recording of the data
- The values (of x and ) are not recorded to consistent decimal places
- There is no evidence of repeats
- There are not enough sets of data (to draw a reliable graph)
- The reading of x at 20.5 does not follow the trend
The student wrote a laboratory report about her investigation.
She reported that the most significant source of error was being unable to judge the
exact point where the ball landed. This was because the ball moved too quickly.
Explain one modification she could make to the apparatus to reduce this error.
You should include additional apparatus.
- Use a camera to record the motion
Which can be viewed in slow motion (to find the exact point where the ball
landed)
OR
- Place a tray of sand on the bench for the ball to land in
So that the ball remains stationary when it lands
Or so the ball leaves an indentation where it lands
To see for time if you don’t use a stop watch you could use a video cam or light gate:
- Use video camera
- Valid method to find time (e.g., count the number of frames)
- Place a light gate (at each marker)
To (start and) stop an electronic/digital timer
Or use a data logger/computer to determine the time
The student added water to the transparent tube to change the length s of the
air column.
Describe a method to determine a single value of s as accurately as possible, using a
metre rule.
- Clamp the metre rule in position
- Check the zero of the metre rule is level with the bottom of the transducer
- View (the metre rule) perpendicularly
- Ensure the metre rule is vertical using a set square
