Physics, 14.04.2020 17:29 jonthedon62

The spaceship Lilac, based on the Purple Planet, is 759 m 759 m long, as measured at rest. When Lilac passes Earth, observers there measure its length to be 688 m 688 m . At what fraction of the speed of light is Lilac moving with respect to Earth?

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Answer from: monstax6

The speed of Lilac is 0.422 times of the speed of light.

Explanation:

Given that,

Length of the spaceship Lilac at rest, $L_o=759\ m$

When Lilac passes Earth, observers there measure its length to be 688 m, L = 688 m

We need to find the speed of light is Lilac moving with respect to Earth. The formula of length contraction is given by :

$L=L_o\sqrt{1-\dfrac{v^2}{c^2}} \\\\\dfrac{v}{c}=\sqrt{1-(\dfrac{L}{L_o})^2} \\\\\dfrac{v}{c}=\sqrt{1-(\dfrac{688}{759})^2} \\\\\dfrac{v}{c}=0.422\\\\v=0.422c$

So, the speed of Lilac is 0.422 times of the speed of light.

Answer from: Quest

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).

Answer from: Quest

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by mathematical calculations before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of uranus led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.

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The spaceship Lilac, based on the Purple Planet, is 759 m 759 m long, as measured at rest. When Lila...

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