Answer:
This is false.
Explanation:
Heat rash develops when some of your sweat ducts clog. Instead of evaporating, perspiration gets trapped beneath the skin, causing inflammation and rash. Heat rash is usually self-limited, meaning it resolves on its own without treatment. Over-the-counter treatments such as calamine, hydrocortisone cream, itch preparations (such as Benadryl spray), or sunburn lotions can be used as skincare to treat the itching and burning symptoms. Heat rash usually goes away on its own within three or four days so long as you don't irritate the site further. Heat rash happens when the sweat glands get blocked. The trapped sweat irritates the skin and leads to small bumps.
The average speed <em>appears to be</em> (distance) / (time) =
(length of the cable) / (time from when a pulse goes in until it comes out the other end) .
That's 1,200,000 meters/ 0.006 second = 2 x 10^8 = <em>2 hundred million m/sec</em>
That figure is about 66.7% of the speed of light in vacuum.
The reason I went through all of this detail was to point out that this is
NOT necessarily the speed of light in this glass, for two reasons.
1). The path of light through an optical fiber is not straight down the middle. In the original fibers of 20 or 30 years ago, the light bounced back and forth off the inside walls of the fiber, and zig-zagged its way along the length. In current modern fibers, it still zig-zags, but it's a more gentle, up-and-down curved path. In either case, the distance covered by the light inside the fiber is more than the straight length of the cable, and the time it takes it to come out the other end is more than its actual speed inside the glass would have meant if it could have traveled straight through the pipe.
2). This problem talks about an optical fiber that's 1,200km long. There is loss in optical fiber, and you're NOT going to get light all the way through a single piece of it that's something like 745 miles long. It takes electronic repeaters, "boosters", and regenerators every few miles to keep it going, and these devices add "latency" or time delay in the process of going through them. That delay in the electronics shows up as apparent delay through the fiber-optic cable, and it makes the speed through the glass appear to be slower than it actually is.
B. velocity is the speed in any given direction.
Answer:
<em>the minimum speed that the ball must have so that the cord does not become slack is</em> <em>2.02 m/s.</em>
<em></em>
Explanation:
In order to avoid slack, the centripetal force of the ball must equal its weight at the top of the circle. Therefore,
F_c = F_g
m v² / r = m g
v² = g r
v = √[g r]
v = √[(9.8 m/s²)(0.417 m)]
<em>v = 2.02 m/s </em>
Therefore,<em> the minimum speed that the ball must have so that the cord does not become slack is</em> <em>2.02 m/s.</em>
<span>Astatine is the limited element found in the Earth's crust. This element is the rarest one found in the crust and it is radioactive. It is named after the Greek word "astatos" which means unstable. The first acknowledgement of it, came in 1940, which was when it was declared.</span>
