OCR GCE AS Level Physics A AS Paper 2 November 2021 question paper H156/02

Two loudspeakers S₁ and S₂ are connected to a signal generator. The loudspeakers emit coherent sound waves.

State what is meant by the term coherent.

A microphone is connected to an oscilloscope. The points O, J, K and L all lie on a straight line as shown. The microphone is moved from O to L.

Not to scale

A series of maxima and minima is observed between O and L. The microphone records a maximum at O. As it moves towards L, the first minimum is observed at J and the next maximum at K. The distance between S₁ and J is 2.00 m and the distance between S₂ and J is 2.08 m. The distance between S₁ and K is 2.05 m and the distance between S₂ and K is 2.21 m.

Calculate the path difference at point J between the waves from S₁ and S₂.

State the phase difference in radian at point J between the waves from S₁ and S₂.

Show that the wavelength of the sound waves is 0.16 m.

The frequency of the sound is determined using the oscilloscope.

Explain how the oscilloscope is used to determine the frequency.

The frequency of the sound is 2.1 kHz.

Determine the speed v of sound.

=........ m s⁻¹ v

The force F against extension x graph below shows the loading and unloading of a piece of

State the physical quantity represented by the area under the loading curve.

Determine the energy E transferred when the rubber is stretched to an extension of 0.25 m.

Suggest why the energy transferred by the rubber during unloading is different to your answer in (ii).

A metal wire has length 2.2 m and cross-sectional area of 1.4 × 10⁻⁷ m². One end of the wire (b) is fixed to the ceiling and a load of weight 49 N is attached to the other end so that the wire is vertical. The Young modulus of the metal is 180 GPa.

The wire obeys Hooke’s law.

Calculate

the stress in the wire

the strain of the wire

the extension x of the wire

the elastic potential energy E of the wire.

The wire in (b) is replaced by a wire of the same metal and length but double the diameter. The same load is attached to the wire.

State and explain the change, if any, to the elastic potential energy of the wire.

* A linear air track is used to investigate the collision of two gliders A and B, as shown in

Light gates 1 and 2 are connected to a data-logger to determine the speed of the gliders. Glider A has a mass of 0.75 kg and glider B has a mass of 1.25 kg.

Two experiments are carried out.

Experiment 1

• Glider B is initially at rest between light gates 1 and 2.

• Glider A passes light gate 1 at a speed of 0.200 m s⁻¹.

• Glider A collides with glider B.

• Glider A rebounds and passes light gate 1 at a speed of 0.050 m s⁻¹ and glider B passes light gate 2 at a speed of 0.150 m s⁻¹.

Experiment 2

• Glider B is initially at rest between light gates 1 and 2.

• Glider A passes light gate 1 at a speed of 0.200 m s⁻¹.

• Glider A collides with glider B.

• Glider A sticks to glider B.

• Both gliders pass light gate 2 at a speed of 0.075 m s⁻¹.

With the help of calculations and the terms below, explain the results of the two experiments.

elastic inelastic momentum

A golf ball initially at rest is hit by a golf club. A data-logger records the variation of force acting on the ball with time t, as shown in Fig. 3.2.

The golf ball has a mass of 0.045 kg.

Calculate the speed v at which the ball leaves the club.

=........ m s⁻¹ v

Show that the cross-sectional area of the wooden cylinder is about 6.6 × 10⁻⁴ m². (a) (i)

Calculate the weight W of the wooden cylinder.

A student places the wooden cylinder in a beaker of water so that it floats. The vertical distance between the water surface and the bottom of the cylinder is y, as shown in Fig. 4.2

The density of water is 1000 kg m⁻³.

Calculate the distance y.

The student repeats the experiment, but replaces the water with oil of density 900 kg m⁻³. The (c) cylinder will still float.

Calculate the new distance y. Explain your answer.

Calculation:

Use Kirchhoff’s second law to show that V = E – I r.

The resistance of the variable resistor is now fixed. The current is 25 mA.

Use the graph to determine the resistance R of the variable resistor.

Calculate the energy W dissipated in the variable resistor in 5.0 minutes.

Calculate the charge Q passing through the variable resistor in 5.0 minutes. Include an appropriate unit.

6* The table shows some of the properties of a light dependent resistor (LDR).

Design a circuit, using a potential divider with the LDR, so that the output potential difference from the circuit is

• greater than 5.0 V when the LDR is in very bright light

• less than 1.0 V when the LDR does not receive any light.

In your answer, include

• a circuit diagram with suggested component values

• an explanation of the operation of the circuit

• how the circuit could be adjusted to change the output potential difference for a different light intensity.

A student investigates the potential difference across a light emitting diode (LED). The student records the wavelength of the light emitted from the LED from a datasheet. The student measures the minimum potential difference V across the LED when the LED first starts to emit light. The student then repeats the experiment for LEDs with different values of . For each value of , the student measures V and determines the absolute uncertainty in V.

The student plots a graph of potential difference V (y-axis) against 1 / (x-axis) including the error bars in V and a straight line of best fit.

It is suggested that the relationship between V and is

where h is the Planck constant, c is the speed of light in a vacuum, e is the elementary charge and D is a constant.

Show that the gradient of the straight line of best fit is about 1.2 × 10⁻⁶ V m. (i)

Use the gradient from (i) to determine a value for h. Write your answer to 2 significant figures.

h =........ J s

Draw a worst acceptable straight line.

Use your worst acceptable straight line to determine the percentage uncertainty in your value for h.

In a different experiment, photoelectrons are emitted from the surface of an aluminium plate when electromagnetic radiation of wavelength 98 nm falls on the plate.

The work function of aluminium is 4.1 eV.

Calculate the maximum kinetic energy KE_max in joules (J) of the photoelectrons emitted from the surface of the aluminium.

The intensity of the electromagnetic radiation falling on the aluminium plate is now decreased without changing its wavelength.

State and explain the change, if any, to the maximum kinetic energy of the photoelectrons.