Unit 9 Test Flashcards
Einstein’s theory of relativity is applicable only in inertial reference frames.
true
Two spaceships A and B are moving relative to an observer O. The spaceships’ gamma values satisfy the relationship gA < gB. Which of the following accurately represents their speeds?
vA < vB
The gamma factor that appears in the special theory of relativity is a function of velocity. Which of the following is the range of values for g?
γ >= 1
An inertial observer O notes that O’ is moving with speed v relative to O. Suppose O measure a time interval delta t. Which of the following should be the corresponding time interval delta t’, based on O’’s clock as calculated by O?
delta t’ = γdelta t
A rod is moving with respect to an observer O, in a direction perpendicular tot he rod’s length. Suppose L0 is the proper length of the rod. Which of the following is the length L of the object measured by O?
L=L0
Suppose the two rods A and B are moving at two speeds (1/4)c and (3/4)c, respectively, relative to an observer O at rest. Both A and B have the same proper length in a given reference frame. Which of the following accurately compares the lengths of A and B as measured by O ?
lA > lB
Suppose two inertial observers are each moving with the speed of light in the opposite directions. What is their relative speed?
c
Two inertial observers are moving with relative speed v. An observer, O, measures the speed of an object in her reference frame to be u and notes O’s speed to be v. What is the speed of the object in the prime inertial frame according to O ?
u’ = u-v/1-uv/c2
An observer in an inertial frame O ′ sees another inertial frame O moving to the right at a speed of (1/3)c. In O, the speed of an object moving to the right is (1/3)c. According to the galilean transformation, O will measure the object’s speed to be (2/3)c. According to the special theory of relativity, what is the speed of the object measured by the observer in O ?
Less than (2/3)c
O observes O ′ move to the right with velocity v. O ′ measures the coordinates, (x ′, t ′ ), of an event. What are the Lorentz transformations that will enable the observer in O ′ to calculate the coordinates of the same event in the O reference frame?
x = γ(x' + vt') y = γ(t' + vx'/c^2)
Suppose two rockets, A and B, are moving to the right as observed in an inertial frame. The velocity of both the rockets is (1/4)c. What is the relative speed of the two rocket ships?
0
Suppose S’ is moving to the right with velocity v = 0.866c as measured by an observer in S. The observer in S’ measures the coordinates of an event: x’ = 2*10^8m and t’ = 0.5s. What is the position and time coordinates of the events as measured by S?
x = 9.2 x 10^8 and t = 2.2s
The coordinates of two events in S are such that delta x > 0. Which of the following condition will guarantee that the corresponding interval delta x’ in S’ is always positive?
delta x > c delta t
Evaluate the following as true or false. According to the special theory of relativity, because v < c, the momentum p = γm0v can never increase without bounds.
false
An object has a rest mass of 2 g. Based on the special theory of relativity, which of the following is the energy equivalent of the object’s mass?
1.8*10^14 J
An observer O notes a particle moving to the right with velocity v. Another observer O ′ is moving with speed v relative to O along the direction of the motion of the particle. Which of the following is the value of the particle’s mass as measured by O and O ′?
O measures m and O’ measures m0
A light particle, or photon, has zero rest mass. Which of the following is incorrect?
The total energy of a photon is zero.
A particle with rest mass m0 = 1.6*10^-16kg is moving at a velocity equal to half the speed of light. Which of the following is the momentum of the particle?
17.3 kg*m^2/s^2
In the relativistic case, which of the following is equal to the kinetic energy when an object is at rest?
0
In Newtonian physics, kinetic energy equals ½ mv 2. Which of the following is the relativistic definition of kinetic energy?
γm0c2 - m0c2
In an isolated system, momentum is conserved. Which of the following is not equivalent to the momentum conservation law?
p = 0
The reference frames A and A′ describe events with unprimed coordinates (x, y) and primed coordinates (x′, y′ ), respectively. Relative to A, A′ moves at a constant speed v in the direction of negative y. If the origins of the two frames coincide at the instant t = 0, which of the following equations correctly relates the coordinates y and y′ ?
y′ = y + vt
P and Q are traveling in the boxcars of two trains that are moving parallel and opposite to each other with relative speed v. Both observers are standing in the middle of their boxcars. As the observers pass each other, as shown in the figure, each turns on a light bulb and the light signal strikes the respective walls on each boxcar. Which of the following statements is not correct?
P notes that the light signal strikes the two ends simultaneously in Q’s car.
Consider the light clock in the figure; the two mirrors are separated by a distance d. A clock tick consists of a roundtrip travel of a light beam from A to B and back to A. Which of the following is the value of d (in miles or meters) for which a tick equals one second
93,000 miles
The proper length and width of a rod are l0 and w0, respectively. To an observer O, the rod is moving to the right with velocity v, as shown in the figure. Which of the following is the length l and width w of the rod measured by O?
l = l0 w = w0/γ
