1. II The wave speed on a string under tension is 200 m/s. What is the speed if the tension is doubled?4. IIII BIO Bats sense objects in the dark by echolocation, in which they emit very short pulses of sound and then listen for their echoes off the objects. A bat is flying directly toward a wall 50 m away when it emits a pulse. 0.28 s later it receives the pulse. What is the bat's speed?8. II A stationary boat in the ocean is experiencing waves from a storm. The waves move at 56 km/h and have a wavelength of 160 m, both typical values. The boat is at the crest of a wave. How much time elapses until the boat is first at the trough of a wave?14. Ill Figure P15.14 shows history graphs of two different points on a string as a wave pulse moves along the string. The blue curve is the history graph for the point at x = 1.0 cm, and the green curve is for the point at x = -3.0 cm. What is the velocity (including the correct sign for its direction) of this wave? Figure P15.14 y (cm) x=-3.0 cm 1 7 -x = 1.0 cm t (s) -2-1 1 2 3 4 5 6 -1