NSAA 2016 Physics S1

• A.effect on frequency: decrease, effect on wavelength: decrease
• B.effect on frequency: decrease, effect on wavelength: increase
• C.effect on frequency: increase, effect on wavelength: decrease
• D.effect on frequency: increase, effect on wavelength: increase
• E.effect on frequency: no effect, effect on wavelength: decrease
• F.effect on frequency: no effect, effect on wavelength: increase

Answer: B

• A.3 alpha
• B.2 alpha and 1 beta
• C.2 alpha and 2 beta
• D.1 alpha and 2 beta
• E.3 beta

Answer: D

A cylindrical copper bar X of length $l$ has a cross-sectional area $A$. The colder end of the bar is kept at temperature $T_1$ and the hotter end is kept at temperature $T_2$.

The curved surface of the bar is perfectly insulated and thermal energy is conducted from the hotter end of the bar to the colder end.

Changes in $l$, $A$, $T_1$ and $T_2$ may alter the rate at which thermal energy is conducted along the copper bar.

In which case is the rate of conduction of thermal energy along the insulated bar the same as for bar X?

• A.change in A: doubles, change in l: no change, change in T1: no change, change in T2: no change
• B.change in A: halves, change in l: no change, change in T1: no change, change in T2: no change
• C.change in A: no change, change in l: doubles, change in T1: no change, change in T2: no change
• D.change in A: no change, change in l: halves, change in T1: no change, change in T2: no change
• E.change in A: no change, change in l: no change, change in T1: decreases by 10°C, change in T2: increases by 10°C
• F.change in A: no change, change in l: no change, change in T1: decreases by 10°C, change in T2: no change
• G.change in A: no change, change in l: no change, change in T1: increases by 10 °C, change in T2: decreases by 10°C
• H.change in A: no change, change in l: no change, change in T1: increases by 10 °C, change in T2: increases by 10°C

Answer: H

The graph shown of quantity $y$ against quantity $x$ represents the motion of a body.

(The scales on both axes are in the appropriate S.I. units, and the gravitational field strength $g$ is $10\,\text{N}\,\text{kg}^{-1}$.)

Which two of the following could the graph represent?

1 kinetic energy against velocity for an object of mass 10kg undergoing free-fall
2 potential energy against height for an object of mass 20 kg being lifted by a constant external force
3 velocity against time for an object of mass 20 kg being accelerated by a resultant force of 100 N
4 work done by an external force of 5N against distance moved for an object of mass 12 kg being moved at constant speed by (and in the direction of) the external force

• 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: F

A uranium-235 nucleus can undergo fission to produce two smaller nuclei.

Which of the diagrams, if any, could represent this process?

• A.none of them
• B.1 only
• C.2 only
• D.3 only
• E.1 and 2 only
• F.1 and 3 only
• G.2 and 3 only
• H.1, 2 and 3

Answer: C

• A.7.2 W
• B.18 W
• C.27 W
• D.45 W
• E.72 W
• F.75 W

Answer: D

The diagram shows a 12V battery, a switch and three resistors. Each resistor has a resistance of 30 $\Omega$.

Initially the switch is open.

What happens to the reading on the ammeter when the switch is closed?

• A.It decreases by 0.20 A.
• B.It decreases by 0.40 A.
• C.It decreases by 0.60 A.
• D.It decreases by 0.80 A.
• E.It increases by 0.20 A.
• F.It increases by 0.40 A.
• G.It increases by 0.60 A.
• H.It increases by 0.80 A.

Answer: E

• A.$2.5 \times 10^{27}$ W
• B.$1.0 \times 10^{28}$ W
• C.$2.0 \times 10^{28}$ W
• D.$2.5 \times 10^{29}$ W
• E.$1.0 \times 10^{30}$ W
• F.$2.0 \times 10^{30}$ W
• G.$2.5 \times 10^{33}$ W
• H.$1.0 \times 10^{34}$ W

Answer: D

• A.900 cm
• B.1200 cm
• C.1800 cm
• D.2400 cm
• E.3600 cm
• F.4800 cm

Answer: E

A motor is used to lift a mass of 5.0 kg using a pulley system as shown in the diagram. The pulley is secured to the roof using a coupling.

The motor needs to cause the mass to accelerate upwards at $0.80\,\text{m}\,\text{s}^{-2}$.

What is the minimum tension force that the coupling must be able to withstand without breaking?

(The gravitational field strength $g$ is $10\,\text{N}\,\text{kg}^{-1}$. The pulley system is frictionless and has negligible mass. The rope has negligible mass and is inextensible.)

• A.4.0 N
• B.8.0 N
• C.46 N
• D.50 N
• E.54 N
• F.92 N
• G.104 N
• H.108 N

Answer: H

A heater is connected in series with a resistor and a 6.0 V battery in the circuit shown.

The total resistance of the circuit is $15\,\Omega$. In 3.0 minutes, 180 J of electrical energy is transferred into other forms in the heater.

How much charge flows through the heater in the 3.0 minutes and what is the voltage across the heater?

• A.charge / C: 1.2, voltage / V: 150
• B.charge / C: 1.2, voltage / V: 216
• C.charge / C: 7.5, voltage / V: 0.041
• D.charge / C: 7.5, voltage / V: 24
• E.charge / C: 72, voltage / V: 0.40
• F.charge / C: 72, voltage / V: 2.5
• G.charge / C: 450, voltage / V: 0.40
• H.charge / C: 450, voltage / V: 2.5

Answer: F

A cubic block has a hole through it with a square cross-section. The dimensions are shown on the diagram. The weight of the block is 30 N.

What is the density of the material from which the block is made?

(The gravitational field strength $g$ is $10\,\text{N}\,\text{kg}^{-1}$.)

• A.$0.30\,\text{g}\,\text{cm}^{-3}$
• B.$0.40\,\text{g}\,\text{cm}^{-3}$
• C.$0.60\,\text{g}\,\text{cm}^{-3}$
• D.$1.2\,\text{g}\,\text{cm}^{-3}$
• E.$3.0\,\text{g}\,\text{cm}^{-3}$
• F.$4.0\,\text{g}\,\text{cm}^{-3}$
• G.$6.0\,\text{g}\,\text{cm}^{-3}$
• H.$12\,\text{g}\,\text{cm}^{-3}$

Answer: F

The diagram shows four solid steel balls P, Q, R and S which are of identical size.
Balls P and R have shiny surfaces. Balls Q and S have dull surfaces.
Balls P and Q are in a room at 20°C. Balls R and S are in a room at 40 °C.
The temperature of each ball at a given moment in time is shown on the diagram.

Which two balls lose thermal energy by convection, and which ball emits thermal radiation at the greatest rate?

• A.lose thermal energy by convection: P and Q, greatest rate of emission of thermal radiation: P
• B.lose thermal energy by convection: P and Q, greatest rate of emission of thermal radiation: Q
• C.lose thermal energy by convection: P and Q, greatest rate of emission of thermal radiation: R
• D.lose thermal energy by convection: P and Q, greatest rate of emission of thermal radiation: S
• E.lose thermal energy by convection: R and S, greatest rate of emission of thermal radiation: P
• F.lose thermal energy by convection: R and S, greatest rate of emission of thermal radiation: Q
• G.lose thermal energy by convection: R and S, greatest rate of emission of thermal radiation: R
• H.lose thermal energy by convection: R and S, greatest rate of emission of thermal radiation: S

Answer: D

The diagram shows the velocity-time graph for an object travelling in a straight line over a period of 30 s.

What total distance did the object travel in the 30s, how far from its starting position was it at the end of the 30s, and what was its average speed over the 30 s?

• A.total distance travelled / m: 90, distance from starting position / m: 70, average speed / ms⁻¹: 3.0
• B.total distance travelled / m: 90, distance from starting position / m: 70, average speed / ms⁻¹: 5.0
• C.total distance travelled / m: 90, distance from starting position / m: 90, average speed / ms⁻¹: 3.0
• D.total distance travelled / m: 90, distance from starting position / m: 90, average speed / ms⁻¹: 5.0
• E.total distance travelled / m: 180, distance from starting position / m: 140, average speed / ms⁻¹: 5.0
• F.total distance travelled / m: 180, distance from starting position / m: 140, average speed / ms⁻¹: 6.0
• G.total distance travelled / m: 180, distance from starting position / m: 180, average speed / ms⁻¹: 5.0
• H.total distance travelled / m: 180, distance from starting position / m: 180, average speed / ms⁻¹: 6.0

Answer: A

A sample of a radioactive isotope X decays to one other radioactive isotope Y. Y has a half-life that is double that of X. Initially only X is present.

Which graph could represent how the numbers of nuclei of X and Y that are present in the sample vary with time?

(All graphs cover the same period of time.)

• A.Graph A
• B.Graph B
• C.Graph C
• D.Graph D
• E.Graph E

Answer: A

• A.$\frac{X}{9X-Y} \times 100$
• B.$\frac{X}{9Y-X} \times 100$
• C.$\frac{Y}{9X-Y} \times 100$
• D.$\frac{Y}{9Y-X} \times 100$
• E.$\frac{X}{9X + Y} \times 100$
• F.$\frac{X}{9Y + X} \times 100$
• G.$\frac{Y}{9X + Y} \times 100$
• H.$\frac{Y}{9Y + X} \times 100$

Answer: G

When a stationary uranium-238 nucleus decays by alpha emission it forms a nucleus of thorium-234. The total kinetic energy produced by the decay is $E$.

What is the kinetic energy of the alpha particle?

• A.$\frac{4E}{238}$
• B.$\frac{4E}{234}$
• C.$\frac{E}{2}$
• D.$\frac{234E}{238}$
• E.$E$

Answer: D

A student carries out an experiment to measure the speed of sound. A loudspeaker that emits sound in all directions is placed between two buildings that are 128 m apart as shown. The student and loudspeaker are 48 m from one of the buildings.

The loudspeaker is connected to a signal generator that causes it to emit regular clicks. The rate at which the clicks are produced is gradually increased from zero until each echo coincides with a new click being emitted by the loudspeaker.

What is the frequency of emission of clicks when this happens?

(The speed of sound in air = $320\,\text{m}\,\text{s}^{-1}$.)

• A.2.0 Hz
• B.2.5 Hz
• C.3.3 Hz
• D.4.0 Hz
• E.5.3 Hz
• F.6.7 Hz
• G.10 Hz

Answer: G