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University Admissions Tests UK (UAT-UK, Pearson VUE) · United Kingdom

NSAA 2016 Section 1 Part B (ESAT Physics)

2016

40 minutes

18 questions. Each part is annotated: check the hint if you are stuck, or reveal the worked solution once you have committed to an approach.

PART B Physics
In the 1920s scientists discovered that the universe is expanding. One consequence of this expansion is that the intense gamma-ray radiation that filled the early universe has now been shifted to the microwave region of the electromagnetic spectrum.

Which line of the table describes how the expansion of the universe has affected the frequency and wavelength of these electromagnetic waves?
Afrequency decreases, wavelength decreases
Bfrequency decreases, wavelength increases
Cfrequency increases, wavelength decreases
Dfrequency increases, wavelength increases
Efrequency has no effect, wavelength decreases
Ffrequency has no effect, wavelength increases
Waves, Sound & the Electromagnetic Spectrum1 mark
A nuclide $_{82}^{214} Pb$ changes by radioactive decay into the nuclide $_{82}^{210} Pb$ .

Which combination of emissions produces this change?
A3 alpha
B2 alpha and 1 beta
C2 alpha and 2 beta
D1 alpha and 2 beta
E3 beta
Radioactivity1 mark
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?
Thermal Physics1 mark
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 $10 N kg^{- 1}$ .)

Which two of the following could the graph represent?

1. kinetic energy against velocity for an object of mass $10 kg$ 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 $5 N$ against distance moved for an object of mass $12 kg$ being moved at constant speed by (and in the direction of) the external force
Energy, Work & Momentum1 mark
A uranium-235 nucleus can undergo fission to produce two smaller nuclei.

Which of the diagrams, if any, could represent this process?
Anone of them
B1 only
C2 only
D3 only
E1 and 2 only
F1 and 3 only
G2 and 3 only
H1, 2 and 3
Radioactivity1 mark
A circuit consists of a $5.0 Ω$ resistor and a variable resistor connected in series with a $24 V$ battery. The variable resistor has a minimum resistance of $3.0 Ω$ and a maximum resistance of $15 Ω$ . The battery and the connecting wires have negligible resistance.

What is the maximum power dissipated in the $5.0 Ω$ resistor?
A $7.2 W$
B $18 W$
C $27 W$
D $45 W$
Electricity & Magnetism1 mark
The diagram shows a $12 V$ battery, a switch and three resistors. Each resistor has a resistance of $30 Ω$ .

Initially the switch is open.

What happens to the reading on the ammeter when the switch is closed?
AIt decreases by $0.20 A$ .
BIt decreases by $0.40 A$ .
CIt decreases by $0.60 A$ .
Electricity & Magnetism1 mark
The total power $P$ radiated by a star is given by: $P = k R^{2} T^{4}$ where $R$ is the radius of the star, $T$ is its surface temperature and $k$ is a constant.

The power currently radiated by the Sun is $4.0 \times 1 0^{26} W$ . Towards the end of the Sun's life its radius will increase by a factor of a hundred and its surface temperature will decrease by a factor of two.

What will be the power radiated by the Sun when these changes have occurred?
Thermal Physics1 mark
A transverse wave travelling through a medium has a frequency of $5.0 Hz$ , a wavelength of $4.0 cm$ and an amplitude of $3.0 cm$ .

What is the total distance travelled by a particle of the medium in one minute?
A $900 cm$
B $1200 cm$
C $1800 cm$
D $2400 cm$
E $3600 cm$
Waves, Sound & the Electromagnetic Spectrum1 mark
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 $0.80 m s^{- 2}$ .

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

(The gravitational field strength $g$ is $10 N kg^{- 1}$ . The pulley system is frictionless and has negligible mass. The rope has negligible mass and is inextensible.)
A
Kinematics & Forces1 mark
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 $15 Ω$ . 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 $1.2 C$ , $150 V$
B $1.2 C$ , $216 V$
Electricity & Magnetism1 mark
A cubic block of side $10 cm$ has a hole of square cross-section, of side $5.0 cm$ , running straight through it from one face to the opposite face. 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 $10 N kg^{- 1}$ .)
illustrative
A $0.30 g cm^{- 3}$
Matter1 mark
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 $20^{\circ} C$ . Balls R and S are in a room at $40^{\circ} C$ .

At a given moment, ball P is at $30^{\circ} C$ , ball Q is at $30^{\circ} C$ , ball R is at $40^{\circ} C$ and ball S is at $40^{\circ} C$ .

Which two balls lose thermal energy by convection, and which ball emits thermal radiation at the greatest rate?
Thermal Physics1 mark
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 $30 s$ , how far from its starting position was it at the end of the $30 s$ , and what was its average speed over the $30 s$ ?
A $90 m$ , $70 m$ , $3.0 m s^{- 1}$
Kinematics & Forces1 mark
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.)
$Five small graphs, labelled A to E, each plotting 'number' (vertical axis) against 'time' (horizontal axis) over the same span of time, with curves for nuclides X and Y individually labelled on each graph. Graph A: X starts high and falls steeply toward zero, flattening out near the axis by the end; Y starts at zero, rises to a rounded peak reaching a bit less than half of X's starting height at roughly a third of the way across, then falls slowly, ending above the X curve. Graph B: X starts high and falls steeply toward zero, similar to graph A; Y starts at zero and rises to a rounded peak that reaches almost as high as X's starting value, a little later than in graph A, then falls, ending above the X curve. Graph C: X starts at a high value and decreases smoothly and monotonically toward zero for the whole interval, without ever peaking; Y starts at zero and increases smoothly and monotonically, curving over to approach a level close to X's starting height by the end, without turning back down; the two curves cross once near the middle of the time span. Graph D: X starts very high and falls very steeply to near zero within the first fraction of the interval, then stays low; Y starts at zero and rises only slightly to a small rounded peak well below half of X's starting height, then decreases slowly; X stays above Y for almost the entire graph except right at the start. Graph E: X and Y both start at the same high value at t = 0; X decreases steadily and relatively quickly toward zero; Y also decreases steadily but more slowly than X, so after the shared starting point Y is always above X; neither curve shows a rise.$
AGraph A: X decays steeply from its initial value toward zero; Y rises from zero to a peak of roughly half of X's initial value, then decays slowly, remaining above X for the rest of the interval.
BGraph B: X decays steeply from its initial value toward zero; Y rises from zero to a peak close to X's initial value, then decays, remaining above X for the rest of the interval.
C
Radioactivity1 mark
Bronze is a mixture of tin and copper.

A particular sample of bronze contains $10%$ tin by volume. (In other words, $10%$ of the total volume of the sample is tin and $90%$ of it is copper.)

What percentage of the mass of the sample is tin?

(Density of tin $= Y$ and density of copper $= X$ .)
A $\frac{X}{9 X - Y} \times 100$
Matter1 mark
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 $\frac{4 E}{238}$
B $\frac{4 E}{234}$
C $\frac{E}{2}$
Energy, Work & Momentum1 mark
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. 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 student notices that each click results in two echoes, one from each building. 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 $= 320 m s^{- 1}$ .)
illustrative
A $2.0 Hz$
Waves, Sound & the Electromagnetic Spectrum1 mark

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PART B Physics