The angle between two plane mirrors that meet at one edge is 45°. The change in direction of a ray that strikes the first mirror at a 60° angle of incidence when that ray reflects from the second mirror is
a. 0°.
b. 45°
c. 90°
d. 150°
e. 270°
d
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Bert says that a charged particle in a vacuum can travel in a helix only if a uniform electric field and a uniform magnetic field are both present and both parallel to the axis of the helix. Stuart says that only a magnetic field with a component parallel to the axis of the helix is needed. Which one, if either, is correct, and why?
a. Bert, because the charged particle's velocity can have a vertical component only if an electric field in the vertical direction is present. b. Stuart, because a component of velocity in the vertical direction is not changed by a vertical component of a magnetic field. c. Bert, because a component of velocity in the vertical direction is changed by a vertical component of a magnetic field. d. Stuart, because an electric field in the vertical direction would cause the particle to come to a complete stop. e. Neither, because particles cannot move in helical paths in the presence of magnetic and electric fields.
Standing Waves on a String: A 4.0-g string is 0.36 m long and is under tension. The string vibrates at 500 Hz in its third harmonic. What is the wavelength of the standing wave in the string?
A. 0.24 m B. 0.36 m C. 0.54 m D. 0.72 m E. 0.90 m
Two hockey pucks are initially at rest on a horizontal plane of frictionless ice. Puck A has twice the mass of puck B. Suppose we apply the same constant force on each puck for the same interval of time dt. How do the puck’s kinetic energies compare at the end of the interval?
A. KA = 4KB B. KA = 2KB C. KA = KB D. KB = 2KA E. KB = 4KA F. Some other relationship (specify)
A step-up transformer has an input voltage of 110 V (rms). There are 100 turns on the primary and 1500 on the secondary. What is the output voltage?
a. 1 600 V (max) b. 1 650 V (rms) c. 3 260 V (max) d. 165 kV (rms) e. 7.3 V (rms)