The horn on a commuter train emits sound with a frequency of 342.5 hz when the train is at rest. the train sounds its horn as it passes a passenger platform at a constant speed of 41 m/s. what overall change in frequency is detected by a person on the platform as the train moves from approaching to receding? remember that change of frequency means the final frequency minus the initial frequency. be sure to include the correct sign on the answer. (take the speed of sound to be 345 m/s.)

Consider a one meter long horizontal pipe with a constant 100 cm^2 cross sectional area. water flows rightward into the pipe at x = 0 with flow velocity 02m/sec at every point within the pipe intake area. at x=1, the rightward flow rate is 0.192 m/sec. assume the water is a conserved quantity in the pipe, so there must be a leak (a sink) somewhere in the pipe. 1. compute net volumetric flow of the source if the system to be in equilibrium. 2. now assume the pipe in the problem has no leaks. compute the net volumetric rate of change for the system.

When doing scientific research ,the sources used should be ?

Dentist's chairs are examples of hydraulic lift systems. if the chair weighs 1,600 n and rests on a piston with a cross-sectional area of 1,440 cm2, what force must be applied to the small piston, which has a cross-sectional area of 72 cm2, to lift the chair?