Modern Physics
Homework #1
Modern Physics 3rd Ed. Serway, Moses, and Moyer- Chapter 1 #12, 20, 26, 27, 28, 31
Problem #7: A relativistic subatomic particle of mass m is moving away from the
detector when it spontaneously decays, sending a photon toward the detector. The photon
is observed to be red shifted by a factor of 100, that is , its energy is 1% of the energy of
the photon measured in the frame where the decaying particle is at rest. What is the speed
of the decaying particle?
Problem #8: An electron has a kinetic energy of 1MeV. What is the radius of curvature
in a uniform magnetic field of 1 T, if the electron velocity is perpendicular to the field?
Problem #9: An observer measures the velocity of two electrons and finds that one has a
speed of c/2 in the x direction and the other has a speed of c/2 in the y direction. What is
the relative speed of the two electrons?
Problem #10: As determined by observer O a red light flashes and 1x10-6 s later, a blue
light flashes 600 m farther out on the x-axis. What are the magnitude and direction of the
velocity of the second observer, O’, if he measures the red and blue flashes to occur
simultaneously?
Problem #11: A rocket ship 150 m long travels at 0.6c. As the tail of the rocket passes by
a man on a stationary platform, he shines a flashlight in the direction of the nose. (a) How
far from the platform is the nose when light reaches it? (b) As measured by the observer
on the space platform, how much time elapses between the emission and arrival of the
light signal? (c) What is the time interval between emission and reception of the signal as
determined by an observer in the nose of the rocket?