I have this question: If the diesel engine coasts at 4.8 km/h into a freight car that is initially at rest, find the speed of the coupled cars. Now I'm looking at the work done, on the answers given but I'm not understanding where the 5.8 coming in to play?

Sawyer is studying diffraction. he draws a diagram of a plane wave to show how light waves travel. which best describes sawyer’s error? the wave fronts should be perpendicular to the direction in which the waves move. the arrow showing the direction of movement of the waves should be pointing to the left. the arrow showing the direction of movement of the waves should be pointing downward. the wave fronts should be both parallel and perpendicular to the direction in which the waves move.

What does si stand for,when referring to a system of measurement

The frequency of the fundamental of the guitar string is 320 hz. at what speed v do waves move along that string?