Due to inertia, perhaps a railroad train in motion should continue moving indefinitely when its engine is turned off. This is not observed because railroad trains
A) aren't massive enough.
B) are too heavy.
C) ride on straight tracks.
D) encounter opposing forces.
Answer: D
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Magnetic Field of a Long Wire: The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 ?T. What is the magnetic field at a distance of 1 cm from this wire?
A. 2 ?T B. 4 ?T C. 6 ?T D. 8 ?T E. 10 ?T
Under which of the following conditions would a car have a westward acceleration?
A) As a car travels eastward with its velocity is increasing. B) A a car travels eastward with its velocity is decreasing. C) As a car travels westward with its velocity is decreasing. D) As a car travels westward with its velocity is constant. E) As a car travels eastward with its velocity is constant.
There is a current I flowing in a clockwise direction in a square loop of wire that is in the plane of the paper. If the magnetic field B is toward the right, and if each side of the loop has length L, then the net magnetic force acting on the loop is
a.
2ILB.
b.
ILB.
c.
IBL2.
d.
zero.
If in the absence of external forces, a rotating ball of hot gas cools and contracts, its rate of rotation
1) decreases 2) remains essentially the same 3) increases and its angular momentum 4) decreases. 5) remains essentially the same. 6) increases.