A heavy ball of mass M is suspended from the ceiling of a car by a light string of mass m (m << M). When the car is at rest, the speed of transverse waves in the string is 60 ms-1. When the car has acceleration a, the wave-speed increases to 60.5 ms-1. The value of a, in terms of gravitational acceleration g, is closest to:

• A. \(\frac{g}{{30}}\)
• B. \(\frac{g}{5}\)
• C. \(\frac{g}{{10}}\)
• D. \(\frac{g}{{20}}\)