Element used in bright flashing signs

The 10-kg double wheel with radius of gyration of 125mm about o is connected to the spring of stiffness k = 600 n/m by a cord which is wrapped securely around the inner hub. if the wheel is released from rest on the incline with the spring stretched 225 mm, calculate the maximum velocity v of its center o during the ensuing motion. the wheel rolls without slipping

How is sound energy produced a. vibrating objects b. objects being heated c. temperature differences d. stationary objects

The material that keeps its new shape after it is stretched is called?