When a guitar string is plucked and the wooden guitar vibrates at the same pitch as the string, this is called a refraction b diffraction c resonance d constructive interference

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

Simple machines can a. increase force only b. decrease force only c. increase or decrease force

What is "decrease in velocity" i need offering 60 !