A 10-m plank is being moved by rolling it over two cylindrical logs placed 2 m from either end of the plank. As the plank is pushed, the logs roll on the ground without slipping, and they do not slip with respect to the plank
How far can the plank be moved before the rear log reaches the end of the plank?
4 m
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Friction: A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30, and the coefficient of kinetic friction is 0.20. What horizontal force must be applied to the box to cause it to start sliding along the surface?
Fill in the blank(s) with the appropriate word(s).
LIGO can detect strong gravitational waves as they pass by because they cause the L-shaped arms of the detector to
A) contract and expand by different amounts. B) become alternately more and less massive. C) experience gravitational time dilation. D) vibrate enough so that the vibrations can be measured with a seismograph.
Deuterium and helium could be made only during the nuclear epoch
Indicate whether the statement is true or false
The diagram shown represents a portion of a wire in a circuit. A current is flowing in the wire in the direction shown. Under the convention that it is positive charge that flows the electric field points in the direction of the current. How can the electric field change direction where the wire bends?
a.
There is an excess of negative charge in the center of the wire.
b.
There is an excess of positive charge at the bottom end of the wire.
c.
There is an excess of negative charge at the right end of the upper portion of the wire.
d.
There is an accumulation of positive charge on the surface, particularly at the bend, such that the sum of electric fields gives the new electric field.
e.
There is an accumulation of electrical potential as the current traverses the wire: The higher potential in the lower half is the source of the field.