AQA A LEVEL PHYSICS PAPER 3 SECTION A
2025/2026 MARKING SCHEME 100%
ACCURATE AMSWERS
What is a set square used for? (5 uses) - ANS-A set square is a right-angled triangle used to:
- Determine whether an object is vertical,
- Determine whether two objects are at right angles to each other,
- Determine whether two lines are parallel,
- Measure the diameter of a circular cross-section (using 2 set squares and a ruler),
- Make sure your eyes are level (reducing parallax error).
NB: similar to a set square, a plumb line or spirit level can be used to test the alignment of an
experimental setup.
Explain a procedure to accurately determine the time period of oscillation. - ANS-- Time over multiple
oscillations (at least 10) using a stop clock.
- Find the mean time period.
- Place a fiducial marker at the centre of oscillation. The mass moves past this point at the greatest
speed so there is the least uncertainty in starting and stopping the stop clock (reducing random errors
due to human reaction time).
- Make sure the amplitude of oscillation is large so that the time period is greater (hence reducing
uncertainty). The initial effect of damping will also be reduced.
- Make sure the system oscillates in one plane.
Describe how a mirror can be used to reduce parallax error. - ANS-A mirror can be used to minimise
parallax error when determining where a pin lines up with a scale. This is done by lining up the pin with
, its own reflection and then taking a measurement. This is particularly useful when reading analogue
meters.
Outline two procedures a student could use to make accurate measurements of the amplitude of
oscillations of either a mass-spring system or a pendulum. - ANS-Mass spring
- Select large initial amplitude to reduce % uncertainty in subsequent values but care needed that the
masses don't fall off the mass holder.
- Select suitable equipment for measurement of amplitude such as a data logger connected to a
computer with a distance sensor positioned underneath the tray or a means of capturing a film or video
of the oscillating tray and masses which includes a scale or ruler to allow determination of amplitude
values.
- Use a large value for mass to increase the time period and hence reduce the % uncertainty in time
measurement.
From A level MS (for a pendulum):
Use a horizontal scale (e.g. ruler).
Use of set square with edge made vertical to eliminate parallax error.
Measure the amplitude from either end of displaced bob.
A steel bar is clamped at the edge of a lab bench. The free end of the bar bends down with deflection y.
Outline an accurate method of determining y, the vertical deflection of the beam, using a metre rule and
any other equipment. - ANS-Clamp a ruler using a stand and a set square to ensure the scale is vertical.
Measure the level of the bar with no load and find the difference in the level for the loaded bar, with
eye level to minimise any parallax error.
From A level MS:
at least one instance seen where a metre ruler is made vertical using a set-square in contact with the
floor
2025/2026 MARKING SCHEME 100%
ACCURATE AMSWERS
What is a set square used for? (5 uses) - ANS-A set square is a right-angled triangle used to:
- Determine whether an object is vertical,
- Determine whether two objects are at right angles to each other,
- Determine whether two lines are parallel,
- Measure the diameter of a circular cross-section (using 2 set squares and a ruler),
- Make sure your eyes are level (reducing parallax error).
NB: similar to a set square, a plumb line or spirit level can be used to test the alignment of an
experimental setup.
Explain a procedure to accurately determine the time period of oscillation. - ANS-- Time over multiple
oscillations (at least 10) using a stop clock.
- Find the mean time period.
- Place a fiducial marker at the centre of oscillation. The mass moves past this point at the greatest
speed so there is the least uncertainty in starting and stopping the stop clock (reducing random errors
due to human reaction time).
- Make sure the amplitude of oscillation is large so that the time period is greater (hence reducing
uncertainty). The initial effect of damping will also be reduced.
- Make sure the system oscillates in one plane.
Describe how a mirror can be used to reduce parallax error. - ANS-A mirror can be used to minimise
parallax error when determining where a pin lines up with a scale. This is done by lining up the pin with
, its own reflection and then taking a measurement. This is particularly useful when reading analogue
meters.
Outline two procedures a student could use to make accurate measurements of the amplitude of
oscillations of either a mass-spring system or a pendulum. - ANS-Mass spring
- Select large initial amplitude to reduce % uncertainty in subsequent values but care needed that the
masses don't fall off the mass holder.
- Select suitable equipment for measurement of amplitude such as a data logger connected to a
computer with a distance sensor positioned underneath the tray or a means of capturing a film or video
of the oscillating tray and masses which includes a scale or ruler to allow determination of amplitude
values.
- Use a large value for mass to increase the time period and hence reduce the % uncertainty in time
measurement.
From A level MS (for a pendulum):
Use a horizontal scale (e.g. ruler).
Use of set square with edge made vertical to eliminate parallax error.
Measure the amplitude from either end of displaced bob.
A steel bar is clamped at the edge of a lab bench. The free end of the bar bends down with deflection y.
Outline an accurate method of determining y, the vertical deflection of the beam, using a metre rule and
any other equipment. - ANS-Clamp a ruler using a stand and a set square to ensure the scale is vertical.
Measure the level of the bar with no load and find the difference in the level for the loaded bar, with
eye level to minimise any parallax error.
From A level MS:
at least one instance seen where a metre ruler is made vertical using a set-square in contact with the
floor
