2024, Prova 1

QUESTION 1 Which option describes a feature of baryons? (A) eliminated by positrons (B) comprised of three quarks (C) a type of elementary particle (D) electrical charge equates to 2 3 e

QUESTION 2 Which property of light is described by the postulates of special relativity? (A) The energy of light is greater when the frequency of the photons decreases. (B) The wavelength of light decreases as the velocity of the source increases. (C) The velocity of light remains constant in all inertial frames of reference. (D) The frequency of light changes depending on media.

QUESTION 3 Two objects with masses 65.0 kg and 75.0 kg respectively are separated by 1.50 m. What is the gravitational force of attraction between them? (A) 3.08 × 10−14 N (B) 3.25 × 10−7 N (C) 2.17 × 10−7 N (D) 1.45 × 10−7 N

QUESTION 4 Two experiments were conducted, and the following observations were made. Experiment 1 Light passing through a double slit produces a diffraction pattern. Experiment 2 Above a specific frequency, light incident on a metallic surface produces photoelectrons with discrete amounts of energy. Which statement can be supported by the observations? (A) A wave theory of light can completely describe the nature of light. (B) The bending of light is a result of light behaving as a particle. (C) The particle model only describes some properties of light. (D) Only light waves can travel in a vacuum.

QUESTION 5 The magnitude of the electrostatic force between two positively charged particles (A) is inversely proportional to the square of the distance between the particles. (B) increases as the square of the distance between the particles increases. (C) is proportional to the square of the distance between the particles. (D) is unrelated to the square of the distance between the particles.

QUESTION 6 The graph shows the relationship between the masses of different objects and the gravitational force they experience on an unknown planet’s surface. Gravitational force (N) Mass (g) 500 0 20 40 60 80 100 120 1000 1500 2000 0 Determine the gravitational field strength for an object at the planet’s surface. (A) 0.02 m s−2 (B) 0.05 m s−2 (C) 20 m s−2 (D) 50 m s−2

QUESTION 7 An object experiencing a gravitational force of 50.0 N moves down a frictionless incline of 40.0° to the horizontal. Calculate the net force acting on the object. (A) 32.1 N (B) 37.3 N (C) 38.3 N (D) 42.0 N

QUESTION 8 An object is pulled in two different directions as shown. 120 N 30 N 60° Not to scale What is the magnitude of the net horizontal force acting on the object? (A) 100 N (B) 90 N (C) 70 N (D) 30 N

QUESTION 9 A passenger at the centre of a train moving at a relativistic speed switches on a light. According to the passenger, light travels outwards as shown. Centre of train Not to scale Direction of travel of train t1 t0 t2 Front Back How would a stationary observer, watching the train pass by them, record this event? (A) Light will reach the back of the train first. (B) Light will reach the front of the train first. (C) Light will reach both ends of the train at t0. (D) Light will reach both ends of the train simultaneously.

QUESTION 10 An experiment was conducted to determine the force experienced by an 85 cm wire with a 2.4 A current flowing through it in an external magnetic field. It was rotated through varying angles within the magnetic field such that data analysis identified the relationship F = 0.0306 sin θ. What is the order of magnitude of the strength of the external magnetic field? (A) 10−4 T (B) 10−2 T (C) 102 T (D) 104 T

QUESTION 11 A planet orbiting a star has an orbital radius of 6.4 × 1014 m and completes a full revolution every 1.5 Earth years. What is the mass of the star? (A) 2.0 × 1017 kg (B) 8.0 × 1018 kg (C) 6.9 × 1040 kg (D) 3.3 × 1048 kg

QUESTION 12 The horizontal displacement of an object experiencing projectile motion was measured and recorded against the cosine of the launch angle (i.e. the angle up from the horizontal). The initial velocity was kept constant. cos θ Horizontal displacement (m) 0.1 0 1 2 3 4 5 6 7 8 0.0 0.3 0.2 0.5 0.4 0.7 0.6 0.8 1.0 0.9 What launch angle would cause the object to land 1.0 m from its starting position? (A) 0.12° (B) 1.0° (C) 6.9° (D) 83°

QUESTION 13 Light with a frequency of 9.4 × 1015 Hz is incident upon an unknown metal, producing photoelectrons with a maximum kinetic energy of 5.6 × 10−18 J. What is the work function of the metal? (A) 1.0 eV (B) 3.9 eV (C) 5.9 eV (D) 6.3 eV

QUESTION 14 Magnetic flux density is a quantity related to the (A) rate of change of field lines moving through a given area. (B) number of magnetic field lines per unit area. (C) volume occupied by a magnetic field. (D) mass–charge ratio of a magnet.

QUESTION 15 In which direction does the centripetal force act? (A) towards the centre of motion (B) away from the centre of motion (C) opposite to the object’s direction of motion (D) tangentially to the object’s direction of motion

QUESTION 16 The table shows a combination of mediating particles and possible forces they experience. Which row is correct? Particle Strong nuclear force Weak nuclear force Electromagnetic force (A) Photon    (B) Lepton   (C) Quark   (D) Meson   

QUESTION 17 A person on Earth experiences a time period of 15 years. Approximately how much time will have passed for a passenger on a spaceship travelling at 0.7 c relative to Earth during that time? (A) 8 years (B) 11 years (C) 21 years (D) 27 years

QUESTION 18 Electromagnetic waves are produced by an oscillating electric charge resulting in an interaction between magnetic and electric fields. How are these two fields aligned? (A) parallel to each other (B) varied in their wavelengths (C) synchronised in their oscillations (D) intersected at the peaks of their amplitudes

QUESTION 19 A 7 µC charge requires 1.5 × 10−8 J of energy to be moved between two points in an electric field. What is the order of magnitude of the potential difference between the two points? (A) 10−2 V (B) 10−3 V (C) 10−9 V (D) 10−13 V

QUESTION 20 Identify the defining feature of a black body. (A) All frequencies of electromagnetic radiation are absorbed and emitted. (B) Light with two wavelength peaks is emitted at a specific temperature. (C) Electrons are emitted in the presence of all frequencies of light. (D) The peak of its spectral output does not vary with temperature.

QUESTION 21 (3 marks) Describe the particle interaction shown. Space Time e− e− e+ e+ γ

QUESTION 22 (5 marks) Special relativity accounts for the observation that more muons from cosmic rays are detected near Earth’s surface than expected. Explain this phenomenon by outlining why Newtonian physics cannot explain this scenario while special relativity can. Refer to the frames of reference of both the travelling muons and the observer near the Earth’s surface.

QUESTION 23 (4 marks) An experiment was conducted to study an object undergoing circular motion, with the radius of motion acting as the independent variable and the speed kept constant. The data comparing the period and radius of motion is shown. Period (s) Radius (m) 0.10 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0.20 0.30 0.40 0.50 0.60 0.00 a) Identify the period expected for a 25 cm radius of motion. [1 mark] Period = s b) Determine the constant speed of the object. Show your working. [3 marks] Speed = m s–1

QUESTION 24 (7 marks) The atomic energy level diagram for an unknown multi-electron ion is shown. Not to scale n = 4 −3.4 eV n = 3 −6.04 eV n = 2 −13.6 eV n = 1 −54.4 eV Ground level a) Calculate the wavelength of light emitted as electrons move from n = 4 to n = 2. Show your working. [4 marks] Wavelength = m A photon with 40.8 eV of energy is incident on the unknown ion and collides with an electron in the first energy level. b) Explain what would happen within the ion in terms of the photon and electron.  [3 marks]

QUESTION 25 (4 marks) A transformer with a turns ratio of 48:1 is set up to reduce a 240 V input. a) Explain how a transformer works in terms of Faraday’s Law and electromagnetic induction.  [3 marks] b) Determine the output voltage. [1 mark] Voltage = V

QUESTION 26 (3 marks) The centres of two small equally positively charged metallic spheres are separated by a distance of 0.30 m and experience a force of 0.025 N between them. Calculate the charge on each of the metallic spheres. Show your working. Charge = C

QUESTION 27 (4 marks) On another planet, an object was projected upwards from an initial height and took 0.71 s to land. 30° Not to scale Object The relationship between vertical displacement (m) and time (s) is sy = −5.18t 2 + 3.5t. Determine the horizontal displacement of the object when it lands. Horizontal displacement = m