When an airplane experiences a tailwind, are the forces added or subtracted? Hint: Tailwind is the term used to describe the air blowing in the direction the plane is going.

Added or subtracted?

cant without the picture! ?

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

answer(20) psi;

3. dark matter

empty space could also be a simple vacuum