What would be the current going through a 200 ohm resister that is connected across a 120 v power supply?

Ascientist notices that an oil slick floating on water when viewed from above has many different colors reflecting off the surface, making it look rainbow-like (an effect known as iridescence). she aims a spectrometer at a particular spot and measures the wavelength to be 750 nm (in air). the index of refraction of water is 1.3

Part of a control linkage for an airplane consists of a rigid member cb and a flexible cable ab. if a force is applied to the end b of the member and causes it to rotate by θ = 0.5°, determine the normal strain in the cable. originally the cable is unstretched.

Ineed to answer this problem but i lack in knowledge, what should i study to answer this problem? i have never used derivatives in a physics problem so i'm not sure what's happening and i can't find videos explaining.