A 3.90 kg weight is placed on top of a vertical spring, which compresses a distance of 2.87 cm. Calculate the force constant (in N/m) of the spring.

in this image, you can see solar radiation going through ocean water.

no image, but probably absorption

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