2025, Prova 2

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1. 

   QUESTION 1 (2 marks) An anti-hydrogen atom is composed of the anti-particles of the corresponding components of a hydrogen atom. A hydrogen atom contains one proton in the nucleus and one electron. Identify two components of an anti-hydrogen atom. 1.   2.  

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2. 

   QUESTION 2 (5 marks) A rock with a mass of 0.15 kg is tied to a piece of string and spun in a horizontal circle in the air. a) Explain how the rock can travel at a constant speed and accelerate at the same time. [2 marks] A force of 4.0 N is exerted on the string, and the rock moves at a constant speed of 6.2 m s−1. b) Calculate the length of the string in metres. Show your working. [3 marks] Length of string = m

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3. 

   QUESTION 3 (5 marks) A spaceship travels at a velocity of 0.8 c towards a distant planet. The spaceship sends a light beam signal to the planet. a) Draw a conclusion about the speed of the signal as seen by observers on the planet. Justify your response.  [2 marks] Observers on the spaceship measure the spaceship’s length as 35 m. b) Calculate the length of the spaceship as seen by observers on the planet. Show your working. [3 marks] Length of spaceship = m

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4. 

   QUESTION 4 (8 marks) An energy level diagram for an atom is shown. Not to scale ionisation 12.3 eV n = 4 9.4 eV n = 3 6.0 eV n = 2 1.8 eV n = 1 0 eV Ground level An electron (ei) transitions from the n = 4 energy level to the n = 2 energy level and emits a photon. a) Calculate the magnitude of the energy change of the electron. [1 mark] Magnitude of energy change = eV A different electron (eii) also transitions from n = 4 to n = 2, but it emits two photons. b) Explain how the transitions of electrons ei and eii result in three different photons. [3 marks] c) Determine the maximum wavelength of a photon that could be produced by the transitions of the two electrons in Questions 4a) and 4b). Show your working. [4 marks] Maximum wavelength = m

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5. 

   QUESTION 5 (5 marks) Three point charges, A, B and C, are set up as shown. 0.060 m A B C 0.140 m +8.4 μC +2.1 μC −4.2 μC Not to scale N S W E Determine the net force acting on charge B. Show your working. Magnitude of net force = N Direction of net force =

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6. 

   QUESTION 6 (11 marks) A current through a wire is coming out of the page. a) Describe the direction and shape of the magnetic field produced by the current-carrying wire. [2 marks] b) Identify the theoretical trend between distance from the wire and magnetic field strength. [1 mark] A 0.90 m wire (wire 1) is placed on an electronic scale which then reads 8.0 × 10−6 kg. A second wire (wire 2) of the same length is secured 0.015 m above wire 1, and has a current of 25 A running through it, as shown. Not to scale Electronic scale Wire 2 Wire 1 I A current is introduced to wire 1 that reduces the reading on the scale to 3.0 × 10−6 kg. c) Determine the magnitude and direction of the current in wire 1. Show your working. [8 marks] Magnitude of current = A Direction of current =

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7. 

   QUESTION 7 (5 marks) A satellite with a mass of 1500 kg orbits the Earth at a height of 6.0 × 105 m above the surface. The radius of the Earth is 6.37 × 106 m. a) Calculate the gravitational force of attraction between the satellite and the Earth. Show your working. [3 marks] Gravitational force = N b) Determine the Earth’s gravitational field strength as experienced by the satellite. Show your working. [2 marks] Gravitational field strength = N kg−1

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8. 

   QUESTION 8 (4 marks) A Feynman diagram is shown. Space Time u d d u d u e− veˇ a) Identify the two quarks that are present in the diagram. [1 mark] 1:  2:  b) Deduce the boson involved in the interaction. [1 mark] c) Describe the significance of symmetry in particle interactions. [2 marks]

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9. 

   QUESTION 9 (5 marks) Describe the ladder in the barn paradox in special relativity. In your response, explain how it is resolved by frames of reference.

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