6. When a mass of 5 kg hangs from a vertical wire of length 2 m, waves travel on this wire with a speed of 10 m/s. What will the speed of these waves be if the length of the wire is doubled? 

A. 20 m/s 

B. 10 m/s 

C. 5 m/s 

D. 40 m/s 

7. If the amplitude in a sound wave is doubled, by what factor does the intensity of the wave increase?

 A. 2 

B. 1 

C. 8 

D. 4 

8. With what tension must a rope with length 2.5 m and mass 0.12 kg be stretched for transverse waves of frequency 40 Hz to have a wavelength of 0.75 m? 

A. 22.1N 

B. 103.4N 

C. 16.8 N 

D. 43.2N