Feb/March 2016

The prefixes nano (n), micro ($\mu$) and pico (p) are often paired with units. Which row gives their correct values?

SI units

A particle of mass $m$, moving at speed $u$, strikes a particle of mass $M$ that is at rest. The velocities of the two particles before and after the collision are illustrated. Which vector diagram shows the momenta correctly before and after the collision?

Linear momentum and its conservation

An object is dropped from rest in a vacuum. The graph shows how the velocity $v$ of the object changes with time $t$. Using the same scales, which graph represents the object falling in air?

Non-uniform motion

The diagram represents a uniform beam PQ. Its length is $3.0\,\text{m}$ and its weight is $50\,\text{N}$. The beam rests on a pivot that is $1.0\,\text{m}$ from end P. A load with weight $W$ is suspended from end P, and the beam is balanced. What is the value of $W$?

Turning effects of forces

At points V and W on an object, two forces of magnitude $F$ each are applied. Together, these forces make a couple. As shown, the object has the form of a right-angled triangle with side lengths $x$ and $y$. Which expression represents the torque produced by the couple?

Turning effects of forces

A giant squid with a length of $20.0\,\text{m}$ is positioned vertically in seawater, and the upper end of the squid is at a depth of $8.00\,\text{m}$. The density of the seawater is $1050\,\text{kg m}^{-3}$. What is the pressure difference between the top and the bottom of the squid?

Density and pressure

An accelerating aircraft is represented in the force diagram. In the instant shown, the aircraft moves at $40\,\text{m s}^{-1}$. At what rate does its kinetic energy increase?

Energy conservation

A man is running along a straight path. What is the approximate value of his kinetic energy?

Gravitational potential energy and kinetic energy

A water pumping system has a pump that takes in $2.0\,\text{kW}$ of electrical power while lifting water. Each second, the system raises $16\,\text{kg}$ of water to a vertical height of $7.0\,\text{m}$. What is the efficiency of the pumping system?

Gravitational potential energy and kinetic energy

A metal wire is extended by a load. The force-extension graph is shown. What does the area beneath the entire graph represent?

Elastic and plastic behaviour

The Young modulus of steel is two times that of copper. A $50\,\text{cm}$ length of copper wire with diameter $2.0\,\text{mm}$ is joined onto a $50\,\text{cm}$ length of steel wire with diameter $1.0\,\text{mm}$, forming a combined wire of length $1.0\,\text{m}$, as illustrated. The combined wire is stretched by a weight attached at its end. Both the copper wire and the steel wire obey Hooke’s law. What is the ratio $\frac{\text{extension of steel wire}}{\text{extension of copper wire}}$ ?

Stress and strain

A crane has an arm with a frictionless pulley fixed to it. A cable runs over the pulley and carries a load of $10\,\text{kN}$ as shown. The crane arm applies a force $F$ to the pulley. What is the value of $F$?

Equilibrium of forces

For which kinds of wave can the Doppler shift be observed?

Doppler effect for sound waves

A star far away is moving away from Earth at a speed of $1.40 \times 10^{7}\,\text{m s}^{-1}$. It gives out light with a frequency of $4.57 \times 10^{14}\,\text{Hz}$. The speed of light is $3.00 \times 10^{8}\,\text{m s}^{-1}$. The Doppler effect formula may be applied to light waves. What frequency will this light have when it is observed on Earth?

Doppler effect for sound waves

The graph illustrates how the displacement of two distinct waves X and Y changes over time. Wave X has frequency $f$ and amplitude $A$. What are the frequency and the amplitude of wave Y?

Progressive waves

Diffraction is the name given to one feature of wave behaviour. What does diffraction enable?

Diffraction

The diagram shows the arrangement of stationary waves produced by the superposition of sound waves from a loudspeaker and the waves reflected from a metal sheet (not shown). W, X, Y and Z are four points on the line passing through the centre of these waves. Which statement about these stationary waves is correct?

Stationary waves

A bugle is a musical instrument made from a long tube with a mouthpiece at one end. The opposite end is open and flared, as illustrated. A musician produces stationary sound waves with a node at the mouthpiece and an antinode at the other end. The lowest frequency of sound that the bugle can produce is $92\,\text{Hz}$. Which other frequencies of sound can the bugle produce?

Stationary waves

Monochromatic light with wavelength $5.30 \times 10^{-7}\,\text{m}$ falls normally on a diffraction grating. The first-order maximum is seen at an angle of $15.4^{\circ}$ to the direction of the incident light. What is the angle between the first-order and second-order diffraction maxima?

The diffraction grating

The diagram illustrates an electron situated in a uniform electric field. In what direction will the field cause the electron to accelerate?

Electric current

At a particular distance from a single alpha particle, the electric field strength is $3.0 \times 10^7\,\text{N C}^{-1}$. What force acts on an electron when it is at that same distance from the alpha particle?

Electric current

Two large parallel plates X and Y are separated by a distance of $5.0\,\text{mm}$ and linked to the terminals of a $200\,\text{V}$ d.c. supply, as shown. At P, a small oil drop has one extra electron. What is the size of the electrostatic force on the oil drop caused by the electric field between the plates?

Potential difference and power

In SI, the unit of specific heat capacity is $\text{J kg}^{-1}\,\text{K}^{-1}$. State the unit of specific heat capacity in SI base units?

SI units

A conductor of electricity has a resistance of $5.6\,\text{k}\Omega$. A potential difference (p.d.) of $9.0\,\text{V}$ is applied across its two ends. How many electrons pass a point in the conductor in one minute?

Electric current

A fixed resistor with resistance $12\,\Omega$ is linked to a battery. The current through the resistor is $0.20\,\text{A}$. The current is then doubled. What is the new power dissipated in the resistor?

Potential difference and power

Which measurements are required to calculate the resistivity of the metal in a piece of wire?

Resistance and resistivity

A $12\,\text{V}$ battery is connected to a source of electromotive force (e.m.f.) and left to charge for $20$ minutes. In this period, the battery receives $7.2 \times 10^4\,\text{J}$ of energy. What quantity of charge flows through the battery?

Potential difference and power

There are three cells with e.m.f.s $V_1$, $V_2$ and $V_3$, each with negligible internal resistance. As illustrated, these cells are linked to three resistors of resistance $R_1$, $R_2$ and $R_3$. The current flowing in the circuit is $I$. Which equation is correct?

Kirchhoff's laws

A network of three resistors, each having resistance $R$, is connected as shown. The combined resistance measured between points X and Y is $8.0\,\Omega$. Determine the value of $R$?

Resistance and resistivity

When obtaining a formula for the total resistance of three resistors connected in series, Kirchhoff’s laws are applied. Which physics principle is used in this derivation?

Kirchhoff's laws

A car battery has an internal resistance of $0.10\,\Omega$ and an electromotive force of $12\,\text{V}$. Once the battery is linked to the starter motor, the potential difference between the battery terminals is $7.0\,\text{V}$. What is the current supplied to the starter motor?

Practical circuits

A sample of an isotope gives off $\beta^-$ particles. These emitted $\beta^-$ particles have a spread of energies. What else has to be emitted?

Atoms, nuclei and radiation

A nucleus of magnesium changes into a nucleus of sodium by releasing a $\beta^+$ particle. The transformation is shown by the equation below. $^{23}_{12}\text{Mg} \rightarrow {}^{P}_{Q}\text{Na} + {}^{0}_{+1}\beta$ Which values are $P$ and $Q$?

Atoms, nuclei and radiation

Quantity $X$ carries a fractional uncertainty of $x$, while quantity $Y$ carries a fractional uncertainty of $y$. What fractional uncertainty applies to $\frac{X}{Y^2}$?

Errors and uncertainties

Thorium-234 ($^{234}_{90}\text{Th}$) undergoes $\beta^-$ emission to form a daughter product, which then undergoes another $\beta^-$ emission to produce a granddaughter product. Which letter in the diagram shows the granddaughter product?

Atoms, nuclei and radiation

PQR and XYZ are wires in a circuit. A galvanometer is connected between Q and Y to act as a null indicator. When the galvanometer shows zero, which statement is correct?

Potential dividers

An object starts with velocity $u$ and moves with acceleration $a$. It travels along a straight path, covers a displacement $s$ and ends with final velocity $v$. These quantities are linked by the equation shown below. $v^2 = u^2 + 2as$ What condition has to be met for this equation to be valid for the object's motion?

Equations of motion

A car is moving at constant velocity. The brakes are then applied, so it undergoes uniform deceleration. Which graph shows how the velocity $v$ of the car varies with distance $s$?

Equations of motion

A ball is projected over level ground. Which statement best describes how the ball moves if air resistance is neglected?

Equations of motion

Which statement gives the definition of force?

Momentum and Newton's laws of motion

The speed $v$ of a transverse wave moving along a uniform string is defined by $v = \sqrt{\frac{Tl}{m}}$, where $T$ is the tension in the string, $l$ denotes its length and $m$ its mass. An experiment is carried out to find the wave speed $v$. The readings are shown in Fig. 1.1.

Progressive waves

Define acceleration in physics.

Equations of motion

State what the term work done means.

Energy conservation

State, with reference to the direction in which energy propagates, what is meant by a transverse wave.

Interference

State the meaning of electric current.

Resistance and resistivity

A neutron undergoes decay by releasing a $\beta^-$ particle.

Fundamental particles

State Newton’s law of gravitation in words.

Gravitational force between point masses

A small coil of wire lies in a non-uniform magnetic field, as illustrated in Fig. 10.1. The coil contains 40 turns of wire and travels in a straight line at constant speed. Its displacement from a fixed point $P$ is $x$. Fig. 10.2 shows how the magnetic flux $\phi$ in the coil varies with $x$.

Electromagnetic induction

State what the threshold frequency means, with reference to the photoelectric effect.

Photoelectric effect

In an X-ray tube, the hardness of an X-ray beam can be controlled.

Production and use of X-rays

Beryllium-7 ($^{7}_{4}\text{Be}$) forms in the upper atmosphere and then falls to the Earth’s surface. Beryllium-7 nuclei decay with a half-life of 53.3 days, producing stable nuclei. A sample of beryllium-7 on a tree leaf has an activity of $39\,\text{mBq}$.

Radioactive decay

State what the term internal energy means.

Kinetic theory of gases

Define specific heat capacity in terms of thermal energy and unit mass.

Specific heat capacity and specific latent heat

An object of mass $80\text{ g}$ carries out simple harmonic motion. The displacement $x$ of the object against time $t$ is illustrated in Fig. 4.1.

Energy in simple harmonic motion

A digital signal is created by taking samples from an analogue signal and then sending those samples through an analogue-to-digital converter (ADC).

Characteristics of alternating currents

A parallel ultrasound beam is normally incident on the surface of a fat layer with thickness $1.1\,\text{cm}$, as illustrated in Fig. 6.1. For the ultrasound, $I_1$ denotes the intensity immediately after the wave enters the fat surface, $I_2$ denotes the intensity incident on the fat-muscle boundary, $I_3$ denotes the intensity reflected from the fat-muscle boundary, and $I_4$ denotes the intensity that returns to the fat surface. Some data for the fat are shown in Fig. 6.2.

Production and use of ultrasound

Define capacitance.

Capacitors and capacitance

State two consequences of negative feedback on the gain of an amplifier that uses an operational amplifier (op-amp).

Characteristics of alternating currents

A particle carrying charge $+q$ and having mass $m$ moves through a vacuum at a steady speed of $1.6 \times 10^5\,\text{m s}^{-1}$. It enters a uniform magnetic field of flux density $9.7 \times 10^{-2}\,\text{T}$, as shown in Fig. 9.1. The magnetic field is perpendicular to the particle’s initial velocity and is also perpendicular to, and out of, the plane of the paper. A uniform electric field is applied in the same region as the magnetic field so that the particle travels through the fields without deviation.

Force on a moving charge