A train is traveling at 30.0 m/sm/s relative to the ground in still air. The frequency of the note emitted by the train whistle is 262 HzHz. The speed of sound in air should be taken as 344 m/sm/s. Part A What frequency fapproachfapproachf_approach is heard by a passenger on a train moving at a speed of 18.0 m/sm/s relative to the ground in a direction opposite to the first train and approaching it

Explanation:

The problem is based on Doppler's effect , for which expression is as follows

n is apparent frequency , n₀ is original frequency , V is velocity of light , v₀ is velocity of observer and v_s is velocity of source , both coming towards each other.

Putting the values

n = 302 .

b) 10 minutes

girls stopped for 10 minutes.

most voltage drop calculators want the distance between the source and destination. then internally, they double it so both the source and return wires are calculated. but you need to know which distance the calculator uses so you're not half of what you should be or double what you should be.

most circuit breakers will not take a #6 directly, so the electrician will have to splice on a smaller pigtail. you also have to upsize the grounding wire when you upsized the ungrounded (hot) wire (see note in 250.122). this will preclude using most cable assemblies, as a cable with #6 copper will most likely only have a #10 grounding conductor. you need a #6 grounding conductor if the circuit is 20a. a #8 cable is no better, as it will have a #10 grounding conductor too. but most 20a breakers will take a #8 directly.

in your related post, you didn't say what type of load this is. if it is a light or heater, voltage drop won't be a big issue. if this is a motor, the current needs are huge at startup and the voltage drop can pose a problem. if this is a motor, knowing if the motor is under much load during startup will answer the voltage drop effect (a saw is easier to start than a compressor).