AQA AS LEVEL PHYSICS Paper 2 2021

AQA AS LEVEL PHYSICS Paper 2 2021. A student investigates stationary waves using microwaves. Figure 1 shows a metre ruler fixed to a bench. The student places a microwave transmitter T at one end of the ruler and a vertical metal reflector R at the other end. R is at a right angle to the ruler. Figure 1 The student places a microwave detector D approximately one-third of the distance from T to R. When T is switched off, the microammeter connected to D reads zero. When T is switched on, stationary waves are produced between T and R, and the microammeter registers a current. When the student moves D along the ruler, the size of the current changes between maximum and minimum values. 3 *03* Turn over ► IB/M/Jun21/7407/2 Do not write outside the box The student measures the current at different positions of D along the ruler to identify a position P of the minimum current. Figure 2 is a plot of the measurements taken near P. Figure 2 0 1 . 1 Draw a line of best fit for these data. [2 marks] 0 1 . 2 State a value for the position of P. [1 mark] position of P = cm Question 1 continues on the next page 4 *04* IB/M/Jun21/7407/2 Do not write outside the box The student moves D along the metre ruler towards R and observes a series of maximum and minimum readings on the microammeter. He identifies Q as the position of the 8th minimum current from P. He measures the distance PQ to be 50.9 cm, as shown in Figure 3. Figure 3 0 1 . 3 The absolute uncertainty in identifying any minimum current is ± 0.2 cm. Determine the percentage uncertainty in the distance PQ. [2 marks] percentage uncertainty in PQ = % 0 1 . 4 Deduce the frequency of the microwaves produced by T. [3 marks] frequency = Hz 5 *05* Turn over ► IB/M/Jun21/7407/2 Do not write outside the 0 1 box . 5 Figure 4 shows D placed at a position where the current is a maximum. Figure 4 The student rotates D by 90°, without changing its distance from T, to the position shown in Figure 5. The current is now zero. Figure 5 State the property of microwaves that is shown by this change in current. [1 mark] 9 6 *06* IB/M/Jun21/7407/2 Do not write outside the 0 2 box A student does an experiment to determine the Young modulus of a metal. Figure 6 shows a wire made from the metal clamped at points A and B so that the wire is horizontal. The horizontal distance between A and B = 3.00 m. C is the mid-point on the wire between A and B. Figure 6 A mass of weight W is suspended at C to extend the wire. Figure 7 shows that C moves vertically downwards by a distance y. Figure 7 7 *07* Turn over ► IB/M/Jun21/7407/2 Do not write outside the 0 2 box . 1 When W is 1.0 N, y is 6.34 cm. Show that the wire extends by approximately 3 mm. [1 mark] 0 2 . 2 Calculate the tension in the wire when W is 1.0 N. [2 marks] tension = N Question 2 continues on the next page 8 *08* IB/M/Jun21/7407/2 Do not write outside the box It can be shown that 2 3 W EAy k y x = + where E = Young modulus of the metal A = 1.11 × 10−7 m2 x = 1.50 m k = a constant. A student measures y for different values of W and plots the graph shown in Figure 8. Figure 8 9 *09* Turn over ► IB/M/Jun21/7407/2 Do not write outside the 0 2 box . 3 Determine E using Figure 8. [4 marks] E = Pa 0 2 . 4 Deduce the fundamental base units for k. [1 mark] fundamental base units for k = 8 10 *10* IB/M/Jun21/7407/2 Do not write outside the 0 3 box Figure 9 shows a micrometer screw gauge used to measure the diameter of a pencil.