Exam-style questions 1 a State what is meant by a reference frame.
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b Discuss the speed of light in the context of Maxwell’s theory.
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c A positive charge q moves parallel to a wire that carries electric current. The velocity of the charged particle is the same as that of the drift velocity of the electrons in the wire.
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q
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Figure A.81 For Exam-style question 1.
a dr
Discuss the force experience by the charged particle from the point of view of an observer: i at rest with respect to the wire. ii at rest with respect to the charged particle.
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2 A rocket moves past a space station at a s speed of 0.98c. The proper length of the space station is 480 m. The origins of the space station and rocket frames coincide when the rocket is moving past the middle of the space station. At that instant clocks in both frames are set to zero. a State what is meant by proper length.
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b Determine the length of the space station according to an observer in the rocket.
c Two lamps at each end of the space station turn on simultaneously according to space station observers, at time zero. Determine i which lamp turns on first, according to an observer in the rocket ii the time interval between the lamps turning on, according to an observer in the rocket.
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d The space–time diagram in Figure A.82 applies to the frames of the space station and the rocket. The black axes represent the space station reference frame. ct / m
ct′ / m
–240
240
ft
x′ / m
x/m
Figure A.82 For Exam-style question 2.
Use the diagram to verify your answer to c i.
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e By drawing appropriate lines on a copy of the space–time diagram, show the events: i ‘light from the lamp at x = 240 m reaches the rocket’. (The rocket is assumed to be a point.) ii ‘light from the lamp at x = −240 m reaches the rocket’. (The rocket is assumed to be a point.) PHYSICS FOR THE IB DIPLOMA © CAMBRIDGE UNIVERSITY PRESS 2014
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