Please help Solve! I need help! Question:
Jermaine runs exactly 2 laps around a 400-meter track. What is the displacement?

Multiple choice answers (I need help I don't understand I don't know what the answer is PLEASE HELP ME):
a. 200
b. 800
c. 400
d. 0

Hydrogen and helium are both members of?

When a vertical beam of light passes through a transparent medium, the rate at which its intensity i decreases is proportional to i(t), where t represents the thickness of the medium (in feet). in clear seawater, the intensity 3 feet below the surface is 25% of the initial intensity i0 of the incident beam. what is the intensity of the beam "10" feet below the surface? (give your answer in terms of i0. round any constants or coefficients to five decimal places.)

Aphoton is absorbed by an electron that is in the n = 3 state of a hydrogen atom, causing the hydrogen atom to become ionized. very far away from the nucleus, the released electron has a velocity of 750,000 m/s. what was the wavelength of the absorbed photon?