A train at rest emits a sound at a frequency of 997 Hz. An observer in a car travels away from the sound source at a speed of 30.9 m/s. What is the frequency heard by the observer? Assume the speed of sound in air to be 346 m/s.
Answer in units of Hz.

Taylor's experiment: 1. accurately measured the speed of light 2. locked together the phases of two light sources so that the interference pattern would not shift 3. showed that man's reaction time was much slower than the speed of light 4. showed that individual photons have wave characteristics

The graph describes the motion of an object. the object moves with from a to b. it from b to c. it moves with from c to d.

The period of a pendulum varies directly as the square root of the length of the pendulum and inversely as the square root of the acceleration due to gravity. find the period when the length is 144 cm and the acceleration due to gravity is 980 cm per second squared, if the period is 7pi seconds when the length is 289 cm and the acceleration due to gravity is 980 cm per second squared.