Gray used a pulley to lift a 300 N object a distance of 3 m. It took Gray 30 seconds to lift the object. How much power did gray exert? A 10 watts
B 20 watts
C 30 watts
D 50 watts

Hydrogen atoms are excited by a laser to the =4n=4 state and then allowed to emit. what is the maximum number of distinct emission spectral lines (lines of different wavelengths) that can be observed from this system? 8 6 2 7 4 5 1 3 calculate the wavelength of the 4⟶14⟶1 transition. =λ=