A small source radiates an electromagnetic wave with a single frequency into vacuum, equally in all directions. As the wave moves, its speed:
1.increases.
2.decreases.
3.stays constant.
3
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A 1000-kg car is moving at 30.0 m/s around a horizontal curve whose radius is 100 m. What is the magnitude of the frictional force required to keep the car from sliding?
A) 9000 N B) 9810 N C) 300 N D) 900 N E) 3000 N
Which of the following is an example of a nonconservative force?
a. gravity b. magnetism c. friction d. Both choices A and B are valid.
A pendulum bob of mass m is set into motion in a circular path in a horizontal plane as shown in the figure. The square of the angular momentum of the bob about the vertical axis through the point P is
a.
m2 gl3 sin4 ?/cos ?
b.
m2 gl3 sin3 ?/cos ?
c.
m2 gl3 sin2 ?/cos ?
d.
m2 gl3 sin ?/cos ?
e.
m2 gl3 sin2 ?
The magnetic field in a region of space is parallel to the surface of a long flat table. Imagine that this page is lying flat on the table. When current is present in the coil, which is lying on the table, the coil tends to rotate so that the left side moves up and the right side moves down. The magnetic field is
a.
directed parallel to the page and downwards.
b.
directed parallel to the page and upwards.
c.
directed parallel to the page and to the right.
d.
directed parallel to the page and to the left.
e.
in a direction that cannot be determined in this experiment