At night, the demand for electricity supplied by a fission nuclear reactor decreases. how is the fission nuclear reaction controlled to avoid overproduction of electricity? the temperature of the reactor is lowered because high temperature and pressure are needed. the temperature of the reactor is raised because the reaction slows down at higher temperatures. the exposure between the fuel rods and a neutron-absorbing material is increased. the exposure between the fuel rods and a neutron-absorbing material is reduced.

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

The frequency of vibrations of a vibrating violin string is given by f = 1 2l t ρ where l is the length of the string, t is its tension, and ρ is its linear density.† (a) find the rate of change of the frequency with respect to the following. (i) the length (when t and ρ are constant) (ii) the tension (when l and ρ are constant) (iii) the linear density (when l and t are constant) (b) the pitch of a note (how high or low the note sounds) is determined by the frequency f. (the higher the frequency, the higher the pitch.) use the signs of the derivatives in part (a) to determine what happens to the pitch of a note for the following. (i) when the effective length of a string is decreased by placing a finger on the string so a shorter portion of the string vibrates df dl 0 and l is ⇒ f is ⇒ (ii) when the tension is increased by turning a tuning peg df dt 0 and t is ⇒ f is ⇒ (iii) when the linear density is increased by switching to another string df dρ 0 and ρ is ⇒ f is ⇒

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c