What distance methods is used to calibrate the Hubble constant?
a. Parallax
b. Supernova observations
c. variable stars
d. both a and b
e. both b and c
E
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Projectile Motion: A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown, assuming negligible air resistance?
A. 6.1 m/s B. 7.4 m/s C. 8.1 m/s D. 8.9 m/s
A 2.0-kg block slides down a plane (inclined at 40° with the horizontal) at a constant speed of 5.0 m/s. At what rate is the gravitational force on the block doing work?
a. +98 W b. +63 W c. zero d. +75 W e. ?75 W
Electrons are used to produce X-rays by allowing a beam of electrons to strike a heavy metal surface. What is true about the wavelengths of the characteristic X-rays that are produced in such a situation?
A. There is a continuous range of wavelengths produced, up to a maximum that depends on the energy of the electron beam used. B. There is a single wavelength of X-ray produced that depends on the energy of the electron beam used. C. There are a few specific wavelengths that are produced for a given metal and their wavelength is independent of the energy of the electron beam used. D. There is a continuous range of wavelengths produced, down to a minimum that depends on the energy of the electron beam used.
The resistance of an object is defined as
A) (length)/(resistivity)(cross-sectional area). B) (current)/(voltage). C) (voltage)/(current). D) (length)(resistivity)(cross-sectional area). E) (voltage)(current).