In order to produce an electric current in a coil of wire, a magnetic field through the coil must be
positive
neutralized
negative
moving

What would the difference of spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 cm on earth, be observed at 21.1 centimeters?

Which component of the earth’s atmosphere is decreased due to photosynthesis?

Aball is thrown horizontally from a cliff at 8m/s .in what direction is the ball moving 2s later?