While standing near a bus stop, a student hears a distant horn beeping. the frequency emitted by the horn is 440 hz. the bus is traveling at 20.0 m/s, and the speed of sound is 330 m/s. what frequency will the student hear at each point in the bus's motion?
a. 468 hz while approaching, 440 hz through the crossing, 415 hz while receding
b. 415 hz while approaching, 440 hz through the crossing, 468 hz while receding
c. 440 hz while approaching, 415 hz through the crossing, 400 hz while receding
d. 505 hz while approaching, 440 hz through the crossing, 438 hz while receding

For problems 1-3, consider a simple dc brush motor with a permanent magnet stator. with an an consider a simple dc brush motor with a permanent magnet ae supply voltage of 100 v, the no-load speed of the motor is 1000 rpm. this motor can provide a torque of 1.9 n-m at 800 rpm drawing a current of 2 a current are both zero at no load.) 1. with an armature supply voltage of 100 v, the motor is operated at 900 rpm. what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input? what is the energy efficiency of the motor? with an armature supply voltage of 100 v, the motor is operated at 1100 rpm (where it acts as a generator). what torque input is required? what mechanical power is required what current is generated? what is the electrical power generated? what is the energy efficiency of the motor acting as a generator? 2. with an armature supply voltage raised to 120 v, the motor is operated at 1000 rpm. what is the no-load speed? what is the motor torque? what is the mechanical power delivered by the motor? what is the current draw? what is the electrical power input what is the energy efficiency of the motor? 3.

Do you agree with scientist’s prediction about the warming of alaska and other polar regions?

Ascientific blank must be testable and capable of being proven false?