Explanation:
Suppose you want to shine a flashlight beam down a long, straight hallway. Just point the beam straight down the hallway -- light travels in straight lines, so it is no problem. What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway is very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.
The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances.
However, some of the light signal degrades within the fiber, mostly due to impurities in the glass. The extent that the signal degrades depends on the purity of the glass and the wavelength of the transmitted light (for example, 850 nm = 60 to 75 percent/km; 1,300 nm = 50 to 60 percent/km; 1,550 nm is greater than 50 percent/km). Some premium optical fibers show much less signal degradation -- less than 10 percent/km at 1,550 nm.
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Mechanical advantage is the amount by which a machine multiplies input force. It is a measure of the force amplification using a tool or machine system.
The momentum of the truck is given by:
p = mv
p = momentum, m = mass, v = velocity
There isn't too much work to do here; the truck is at rest, therefore its velocity is 0. This means the product of m and v is 0, giving the momentum as 0.
This is the same question that I just answered.
Have present the definition of acceleration:
a = Δv / Δt, this is change in velocity per unit of time.
a and v are in bold to mean that they are vectors.
1) a body traveling in a straight line and increasing in speed: CORRECT:
Acceleration is the change in velocity, either magnitude or direction or both. So, a body increasing in speed is accelerated.
2) a body traveling in a straight line and decreasing in speed: CORRECT
A decrease in speed is a change in velocity, so it means acceleration.
3) a body traveling in a straight line at constant speed: FALSE.
That body is not changing either direction or speed so its motion is not accelerated but uniform.
4) a body standing still : FALSE.
That body is not changind either direction or speed.
5) a body traveling at a constant speed and changing direction: CORRECT.
The change in direction means that the body is accelerated. The acceleration due to change in direction is named centripetal acceleration.
