What was most surprising about SN1987A?
A) Its pulsar appeared within weeks of the explosion.
B) The supernova was luminous enough to see with the naked eye.
C) The supernova was not even in our own Galaxy.
D) The parent star was a blue supergiant, much like Deneb or Rigel.
E) It did not produce the flood of neutrinos our models had led us to expect.
D
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A measurement of an electron's speed is 2.0 × 106 m/s and has an uncertainty of 10%. What is the minimum uncertainty in its position? (h = 6.626 × 10-34 J ? s, mel = 9.11 × 10-31 kg)
A) 0.91 nm B) 1.8 nm C) 2.7 nm D) 2.8 nm E) 5.0 nm
All the following may be represented by vectors except
a. velocity. b. acceleration. c. speed. d. displacement.
If the displacement of an object is given in SI units by Dx = -5t + t 2, at t = 2 s its velocity and acceleration are, respectively: (Hint: Use dimensional analysis along with the equations for motion with constant acceleration.)
a. positive, positive. c. negative, negative. b. positive, negative. d. negative, positive.
It is often possible to use atomic masses when calculating the binding energy of a nucleus. This is not true for calculating the Q value for the e+ decay process since
a. the electron masses do not cancel. b. a positron is an antiparticle. c. the electron masses cancel. d. the mass of a positron cannot be neglected when compared to the mass of a nucleus. e. none of the above.