Two positively charged objects are separated by a large distance. One of the positively charged objects is replaced by a negatively charged object, and the two
objects are moved closer to each other.
Which of the following occurs in this situation?
a.
The attractive force becomes a repulsive force, which increases as the objects move closer
together.

B.
The repulsive force becomes an attractive force, which increases as the objects move closer to
each other.
C.
The attractive force becomes a repulsive force, which decreases as the objects move closer to
each other.
D.
The repulsive force becomes an attract
creases as the objects move closer to
each other.

Acommon procedure for measuring the velocity of an airstream involves the insertion of an electrically heated wire (called a hot-wire anemometer) into the airflow, with the axis of the wire oriented perpendicular to the flow direction. the electrical energy dissipated in the wire is assumed to be transferred to the air by forced convection. hence, for a prescribed electrical power, the temperature of the wire depends on the convection coefficient, which, in turn, depends on the velocity of the air. consider a wire of length l = 20 mm and diameter d = 0.5 mm, for which a calibration of the form v = 6.25 ă— 10â’5 h2 has been determined. the velocity v and the convection coefficient h have units of m/s and w/m2 â‹… k, respectively. in an application involving air at a temperature of tâž = 25â°c, the surface temperature of the anemometer is maintained at ts = 75â°c with a voltage drop of 5 v and an electric current of 0.1 a. what is the velocity of the air?