What type of wave can be seen by the human eye

If you have a bowl with six apples and you take away four, how many do you have? anyone take a guess and post it. lol getting rid of my account might as well do it with some fun

Will give brainliest! jay rides his 2.0-kg skateboard. he is moving at speed 5.8 m/s when he pushes off the board and continues to move forward in the air at 5.4 m/s. the board now goes forward at 13 m/s.a. determine jay’s mass.b. determine the change in the internal energy of the system during this process.(express your answer to two significant figures and include the appropriate units.)

The pressure proportional to the area a- inversely b- directly c- increase d-decrease