An astronomer observes a hydrogen line in the spectrum of a star. the wavelength of hydrogen in the laboratory is 6.563 x 10-7m, but the wavelength in the star's light is measured at 6.56186 x 10-7m. which of the following explains this discrepancy? a. the star is moving away from earth b. the wavelength of light that the star is emitting changes constantly. c. the frequency of light that the star is emitting changes constantly. d. the star is approaching earth.

(2) (a) you have a simple circuit that consists of only a battery (δvbat=1.5v) and two resistors with resistance r1=10ω and r2=5ω, connected in series with each other. what is the current running through the battery? (b) you re-arrange your circuit so now r2 is attached in parallel to r1 rather than in series. what is the current running through the battery? (c) you add an additional resistor r3=7ω on the same branch as r2. what is the current running through the battery? (d) what is the power dissipated in r3?

If an electric circuit is not grounded it is best to reach out and touch it to provide the ground a.true or b.false

Friction removes energy from objects in motion. which statement best describes how this works? a) friction transforms ke into thermal energy b) friction transfers thermal energy to ke c) friction transforms te into pe d) friction transforms pe into ke e) friction transfers ke into pe