NSAA 2022 Physics PART B

• A.0.0060 N
• B.0.36 N
• C.0.60 N
• D.0.81 N
• E.36 N
• F.49 N
• G.81 N
• H.4900 N

Answer: A

A rider on a rollercoaster moves very quickly towards a solid wall. While moving, the rider shouts, and hears an echo of the shout from the wall. The echo is quieter than the original shout.

How do the amplitude and frequency of the echo heard by the rider compare to the amplitude and frequency of the original shout?

• A.lower, lower
• B.lower, unchanged
• C.lower, higher
• D.unchanged, lower
• E.unchanged, higher
• F.higher, lower
• G.higher, unchanged
• H.higher, higher

Answer: C

The diagram shows a system consisting of two large copper tanks of water connected to each other by a solid cylindrical copper bar.

The temperature of the water in tank 1 is $T_1$. The water in tank 2 is at a higher temperature $T_2$. At all times $T_1 < T_2$.

The following four statements list changes that can be made, independently, to the system.

1 increase temperature $T_1$
2 increase temperature $T_2$
3 increase the length of the copper bar
4 increase the diameter of the copper bar

Which two changes each independently result in an increase in the rate of conduction of thermal energy along the copper bar?

• A.1 and 2
• B.1 and 3
• C.1 and 4
• D.2 and 3
• E.2 and 4
• F.3 and 4

Answer: E

• A.0.025 C
• B.0.050 C
• C.0.15 C
• D.0.30 C
• E.0.75 C
• F.1.5 C
• G.9.0 C
• H.18 C

Answer: G

• A.0.0010 N
• B.1.0 N
• C.1.5 N
• D.100 N
• E.150 N
• F.1500 N

Answer: E

• A.12 J
• B.20 J
• C.24 J
• D.32 J
• E.40 J
• F.64 J

Answer: B

Ultrasound is used to find a crack inside a cuboid block of metal. An ultrasound probe is held in contact with the top surface of the metal block and perpendicular to the surface. A short pulse of ultrasound is sent into the metal block at time $t = 0$ ms and reflects from both the crack and the bottom surface of the metal block.

The times between the emission of the ultrasound pulse and the return of the reflections to the probe, and the strengths of the reflected pulses, are measured. The results are shown on the graph.

The speed of ultrasound in the metal is $5000 \text{ m s}^{-1}$.

What is the distance between the bottom surface of the metal block and the crack?

• A.0.2 m
• B.0.3 m
• C.0.4 m
• D.0.5 m
• E.0.6 m
• F.1.0 m

Answer: A

• A.0.160 J
• B.0.240 J
• C.160 J
• D.240 J
• E.576 J
• F.864 J
• G.576 000 J
• H.864 000 J

Answer: G

The diagram shows a circuit that includes two ammeters and a resistor R.

The readings on the ammeters are shown.

What is the resistance of resistor R?

• A.0.40 Ω
• B.2.5 Ω
• C.3.0 Ω
• D.3.6 Ω
• E.5.5 Ω
• F.8.5 Ω

Answer: B

The graph shows potential difference plotted against current for a filament lamp and a resistor.

The lamp and the resistor are connected in parallel with each other to a 6.0 V power supply and the current in the lamp, $I$, is recorded.

In a second circuit, the lamp and the resistor are now connected in series with each other to the same power supply, and the current in the resistor is 0.18 A. The potential difference across the lamp, $V$, is recorded.

What are the values of $I$ in the first circuit and $V$ in the second circuit?

• A.$I=0.25 \text{ A}$, $V=1.6 \text{ V}$
• B.$I=0.25 \text{ A}$, $V=3.0 \text{ V}$
• C.$I=0.25 \text{ A}$, $V=4.4 \text{ V}$
• D.$I=0.35 \text{ A}$, $V=1.6 \text{ V}$
• E.$I=0.35 \text{ A}$, $V=3.0 \text{ V}$
• F.$I=0.35 \text{ A}$, $V=4.4 \text{ V}$

Answer: D

• A.1.6 N
• B.3.2 N
• C.4.8 N
• D.6.4 N
• E.8.0 N

Answer: E

A transverse wave on a string has a speed of $500 \text{ m s}^{-1}$.

The horizontal distance between two points P and Q on the wave is 4.0 m, as shown in the diagram.

At time $t = 0$ ms, point X on the string is at its maximum displacement of 6.0 mm above equilibrium.

What is the displacement of point X at time $t = 7.0$ ms?

• A.6.0 mm above equilibrium
• B.between 0 mm and 6.0 mm above equilibrium
• C.0 mm
• D.between 0 mm and 6.0 mm below equilibrium
• E.6.0 mm below equilibrium

Answer: C

A neutral atom Q of a particular element contains a total of 20 particles (protons, neutrons and electrons).

The table shows information about the number of particles and relative charges of four atoms or ions W, X, Y and Z.

Which of these atoms or ions could be of a different isotope to Q but of the same element as Q?

• A.W only
• B.X only
• C.Z only
• D.X and Z only
• E.W and Y only
• F.W, X and Y only
• G.W, Y and Z only
• H.X, Y and Z only

Answer: G

Radioactive isotope X undergoes a single beta ($\beta^−$) decay to form the stable isotope Y.

A sample consists only of X and Y. The graph shows how the mass of Y present in the sample varies with time. After a long time, the mass of Y in the sample becomes a constant 50 g.

What is the half-life of X?

• A.0.6 minutes
• B.1.2 minutes
• C.2.0 minutes
• D.3.2 minutes
• E.4.0 minutes
• F.5.2 minutes

Answer: C

A piece of metal of mass 50 g is at thermal equilibrium in a hot liquid at temperature $T$.

The metal is removed from the liquid and immediately placed in 100 g of water that is at 20 °C.

The water is stirred and reaches a final temperature of 26 °C.

What is the temperature $T$ of the hot liquid?

(Assume that heat transfers to or from the surroundings are negligible.)

• A.38 °C
• B.51 °C
• C.150 °C
• D.170 °C
• E.480 °C

Answer: D

A bar magnet is placed at position X close to one end of a coil and on the axis of the coil as shown.

The graph shows how the velocity of the magnet varies as it is then moved rapidly to position Y and back to position X.

The magnetic field of the bar magnet still affects the coil when the magnet is at position Y.

Which graph represents how the induced voltage in the coil changes as the magnet moves?

• A.[Graph A shows a negative rectangular pulse, then a positive rectangular pulse of smaller height and longer duration.]
• B.[Graph B shows a negative voltage decreasing linearly to zero, then a positive voltage increasing linearly to a smaller peak.]
• C.[Graph C shows a negative rectangular pulse followed by zero voltage.]
• D.[Graph D shows a negative voltage that decreases in magnitude, then a positive voltage that decreases in magnitude.]
• E.[Graph E shows a curved negative pulse followed by a curved positive pulse.]
• F.[Graph F shows a sharp negative spike, then a sharp positive spike of smaller magnitude.]

Answer: D

A small slider of mass 30 g is at rest near the bottom of a frictionless slope and in contact with a light uncompressed spring as shown.

[diagram not to scale]

The spring is compressed by 5.0 cm and the slider remains in contact with it.

The spring is released and causes the slider to rise up the slope to a maximum vertical height of 20 cm.

The slider is replaced with one of mass 20 g.

The spring is now compressed by 15 cm, and the new slider remains in contact with it.

To what maximum vertical height does this new slider rise after it is released?

(the spring obeys Hooke's law; assume that air resistance is negligible)

• A.40 cm
• B.60 cm
• C.90 cm
• D.120 cm
• E.180 cm
• F.270 cm

Answer: F

• A.$0.960 \text{ kg m}^{-3}$
• B.$1.20 \text{ kg m}^{-3}$
• C.$1.25 \text{ kg m}^{-3}$
• D.$1.28 \text{ kg m}^{-3}$
• E.$1.50 \text{ kg m}^{-3}$
• F.$4.80 \text{ kg m}^{-3}$

Answer: E

• A.60 km
• B.90 km
• C.135 km
• D.150 km
• E.225 km

Answer: E

• A.$0.40 \text{ N cm}^{-2}$
• B.$1.2 \text{ N cm}^{-2}$
• C.$3.2 \text{ N cm}^{-2}$
• D.$6.4 \text{ N cm}^{-2}$
• E.$8.0 \text{ N cm}^{-2}$

Answer: A