Why are folded mountains evidence of plate tectonics?

***smaller giveaway***

In automobile steering wheel is shown what is the ideal mechanical advantage blank? if the ama is eight what is the efficiency of the steering wheel?

Explain why electric current cannot exist if a current doesn't have a voltage source.

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=