When you drag a toy teddy bear along the floor by a force that is parallel to the floor, the magnitude of the force of friction
a. is independent of velocity or acceleration.
b. increases when the velocity increases.
c. is proportional to the acceleration.
d. decreases when the force parallel to the floor increases.
e. increases when the force parallel to the floor increases.
a
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Two stars with about the same mass are found to have transiting planets with similar semi-major axes. Star 1 exhibits a Doppler shift twice as large as Star 2. What can we determine about these two systems?
A) The planet around Star 2 is more massive than the planet around Star 1. B) The planet around Star 1 has a thicker atmosphere than the planet around Star 2. C) The planet around Star 1 is more massive than the planet around Star 2. D) The planet around Star 2 has a thicker atmosphere than the planet around Star 1.
The light-gathering power of a telescope is directly proportional to the:
A) square of the diameter of the primary mirror or lens. B) cube of the diameter of the primary mirror or lens. C) square of the focal length of the primary mirror or lens. D) cube of the radius of curvature of the primary mirror or lens.
Magnetic Field of a Long Wire: A long straight wire carrying a 4-A current is placed along the x-axis as shown in the figure. What is the direction of the magnetic field at a point P due to this wire?
A. into the plane of the page B. out of the plane of the page C. along the -x-axis D. along the +x-axis E. along the +y-axis
Loop A and a long, straight, current-carrying wire lie near each other on a tabletop in the top view shown below. Loop B is oriented perpendicular to the wire. 
Suppose that the current in the wire suddenly decreases. In what direction does the induced current flow in
A. Clockwise. B. Counterclockwise. C. No current flows in this loop. D. One needs more information to answer.