How does the Doppler effect explain why a siren's pitch increases as it approaches you? A. The siren moves away from sound waves it has already produced, increasing their wavelength.
B. The siren moves closer to sound waves it has already produced) decreasing their wavelength
C. The siren moves away from sound waves it has already produced decreasing their wavelength,
D. The siren moves closer to sound waves it has already produced, increasing their wavelength

What are the necessary conditions for fusion?

If a car is traveling on the highway at a constant velocity, the force that pushes the car forward must be a. equal to the weight of the car. b. less than the force of friction exerted upon the car. c. equal to the force of friction exerted upon the car. d. greater than the weight of the car.

Aspring has a relaxed length of 33 cm (0.33 m) and its spring stiffness is 6 n/m. you glue a 76 gram block (0.076 kg) to the top of the spring, and push the block down, compressing the spring so its total length is 15 cm. you make sure the block is at rest, then at time t=0 you quickly move your hand away. the block begins to move upward, because the upward force on the block by the spring is greater than the downward force on the block by the earth. calculate y vs. time for the block during a 0.09-second interval after you release the block, by applying the momentum principle in three steps each of 0.03-second duration.