A rocket moving with speed v relative to the ground emits a flash of light in the backward direction. An observer in the rocket measures the speed of the flash of light to be c.
State the speed of the flash of light according to an observer on the ground using Galilean relativity.
State the speed of the flash of light according to an observer on the ground using Maxwell's theory of electromagnetism.
State the speed of the flash of light according to an observer on the ground using Einstein's theory of relativity.
Two rockets, A and B, are moving towards each other on the same path. From the frame of reference of the Earth, an observer measures the speed of A to be 0.6c and the speed of B to be 0.4c. According to the observer on Earth, the distance between A and B is 6.0 × 10^8 m.
Define frame of reference.
Calculate, according to the observer on Earth, the time taken for A and B to meet.
Identify the terms in the formula.
Determine, according to an observer in A, the velocity of B.
Determine, according to an observer in A, the time taken for B to meet A.
Deduce, without further calculation, how the time taken for A to meet B, according to an observer in B, compares with the time taken for the same event according to an observer in A.
Rocket and rocket are travelling in opposite directions from the Earth along the same straight line. In the reference frame of the Earth, the speed of rocket is and the speed of rocket is .
Calculate, for the reference frame of rocket A, the speed of rocket B according to the Galilean transformation.
Calculate, for the reference frame of rocket A, the speed of rocket B according to the Lorentz transformation.
Outline, with reference to special relativity, which of your calculations in is more likely to be valid.
A train of proper length 85 m moves with speed 0.60c relative to a stationary observer on a platform.
Define proper length.
In the reference frame of the train a ball travels with speed 0.50c from the back to the front of the train, as the train passes the platform. Calculate the time taken for the ball to reach the front of the train in
the reference frame of the train.
the reference frame of the platform.
An object of mass 1 kg is thrown downwards from a height of 20 m. The initial speed of the object is .
The object hits the ground at a speed of . Assume . What is the best estimate of the energy transferred from the object to the air as it falls?
One of the postulates of special relativity states that the laws of physics are the same in all inertial frames of reference.
State what is meant by inertial in this context.
An observer is travelling at velocity v towards a light source. Determine the value the observer would measure for the speed of light emitted by the source according to Maxwell's theory.
An observer is travelling at velocity v towards a light source. Determine the value the observer would measure for the speed of light emitted by the source according to Galilean transformation.
The diagram shows the motion of the electrons in a metal wire carrying an electric current as seen by an observer X at rest with respect to the wire. The distance between adjacent positive charges is d.
State whether the field around the wire according to observer X is electric, magnetic or a combination of both.
Observer Y is at rest with respect to the electrons.
Discuss the change in d according to observer Y.
Deduce whether the overall field around the wire is electric, magnetic or a combination of both according to observer Y.
This question is about a light clock.
One of the postulates of special relativity refers to the speed of light. State the other postulate of special relativity.
In a light clock, a beam of light is reflected between two parallel mirrors M1 and M2.
stationary observer
The time interval between successive reflections at M2 according to an observer at rest relative to the light clock is t. This light clock is moving at velocity v relative to the stationary observer.
Show that the time t' between successive reflections at M2 in this light clock as measured by the stationary observer is t' = t / sqrt(1 - v^2/c^2).
Using the axis, sketch a graph to show how the ratio t'/t varies with v. You should add key values to your graph.
Maxwell's equations led to the constancy of the speed of light. Identify what Maxwell's equations describe.
State a postulate that is the same for both special relativity and Galilean relativity.
Two parallel current-carrying wires have equal currents in the same direction. There is an attractive force between the wires. Identify the nature of the attractive force recorded by an observer stationary with respect to the wires.
A second observer moves at the drift velocity of the electron current in the wires. Discuss how this observer accounts for the force between the wires.
An observer on Earth watches rocket A travel away from Earth at a speed of 0.80c. The spacetime diagram shows the worldline of rocket A in the frame of reference of the Earth observer who is at rest at x = 0. Another rocket, B, departs from the same location as A but later than A at ct = 1.2 km according to the Earth observer. Rocket B travels at a constant speed of 0.60c in the opposite direction to A according to the Earth observer.
Draw on the spacetime diagram the worldline of B according to the Earth observer and label it B.
Deduce, showing your working on the spacetime diagram, the value of ct according to the Earth observer at which the rocket B emitted its flash of light.
Explain whether or not the arrival times of the two flashes in the Earth frame are simultaneous events in the frame of rocket A.
Calculate the velocity of rocket B relative to rocket A.