Select the correct answer 1. Instruments that produce sound are called sources of light.

2. Music has no ability to heal the mental stress.

3. A medium is necessary for sound travel.

4. We hear sounds of frequencies below 20 Hz. O First answer O Second answer O Third answer O Forth answer

Awind turbine is rotating counterclockwise at 0.5 rev/s and slows to a stop in 10 s. its blades are 20 m in length. (a) what is the angular acceleration of the turbine? (b) what is the centripetal acceleration of the tip of the blades at t=0s? (c) what is the magnitude and direction of the total linear acceleration of the tip of the blades at t=0s?