He inner surface of a cone coated by a reflecting layer forms a conical mirror. a thin incandescent filament is stretched in the cone along its axis aphe minimum angle o of the cone for which the rays emitted by the filament will be reflected from the conical surface not more than once is greater than or equal to 120°. b) ifangle ofcone is less than 120° the rays from the filament will be reflected from the conical surface not more than once c) forany angle of cone multiple reflections of the rays from filament occurs d) lf angle ofcone is less than 120° the rays from the filament will be reflected from the conical surface more than once

Abug is 12 cm from the center of a turntable that is rotating with a frequency of 45 rev/min . what minimum coefficient friction is required so that the bug stays on the turntable?

Phase changes are chemical changes. true or false

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 ⇒