Parallel Wires: A ring with a clockwise current (as viewed from above the ring) is situated with its center directly above another ring, which has a counter-clockwise current, as shown in the figure. In what direction is the net magnetic force exerted on the top ring due to the bottom ring?
A. upward
B. downward
C. to the left
D. to the right
E. The net force is zero.
Answer: A
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The output voltage of an AC generator is of the form V = V0 sin(2?ft). A typical frequency in household circuits is 60 Hz. Using radians for angular measure in this equation, what is the factor 2?f in radians per second for this frequency?
a. 2? b. 120 c. 377 d. 60
Car A rear ends Car B, which has twice the mass of A, on an icy road at a speed low enough so that the collision is essentially elastic. Car B is stopped at a light when it is struck. Car A has mass m and speed v before the collision. After the collision
a. each car has half the momentum. b. car A stops and car B has momentum mv. c. car A stops and car B has momentum 2mv. d. the momentum of car B is four times as great in magnitude as that of car A. e. each car has half of the kinetic energy.
A 3.00 g lead bullet is traveling at a speed of 300 m/s when it embeds in a wood post. If we assume that half of the resultant heat energy generated remains with the bullet, what is the increase in temperature of the embedded bullet? (specific heat of lead = 0.0305 kcal/kg• °C, 1 kcal = 4186 J)
a. 113°C c. 176°C b. 137°C d. 259°C
Our galaxy is suspected to be surrounded by a galactic halo or corona because the disk of the galaxy
a. rotates faster than expected in its outer region. b. rotates more slowly than expected in its outer region. c. is only visible during a total eclipse of our Sun. d. is surrounded above, below, and well beyond by the brightly glowing corona.