Answer: 
Explanation:
When a number is written in scientific notation (representing the number using powers of base ten) it is expressed so that it contains a digit in the place of the units and all other digits after the decimal point, multiplied by the respective exponent.
Then, the significant figures (or significant digits) will be the digits that are before the power of ten.
Now, in the case of the number 299,792,458 if we want to write it with three significant digits, we have to write it in scientific notation as:

Answer:
Explanation:
1- Density increase as the temperature decreases. This is the reason why liquid water is more dense than solid water.
2- The only things that affect the period of a simple pendulum are its length and the acceleration due to gravity.
3- not really sure for that one...I will think about that.
4- same reason for number 3
Answer:
B) I1 = 1680 kg.m^2 I2 = 1120 kg.m^2
C) V = 0.84m/s T = 29.92s
D) ω2 = 0.315 rad/s
Explanation:
The moment of inertia when they are standing on the edge:
where M is the mass of the merry-go-round.
I1 = 1680 kg.m^2
The moment of inertia when they are standing half way to the center:

I2 = 1120 kg.m^2
The tangencial velocity is given by:
V = ω1*R = 0.84m/s
Period of rotation:
T = 2π / ω1 = 29.92s
Assuming that there is no friction and their parents are not pushing anymore, we can use conservation of the angular momentum to calculate the new angular velocity:
I1*ω1 = I2*ω2 Solving for ω2:
ω2 = I1*ω1 / I2 = 0.315 rad/s
Answer:
Optical Time Domain Reflector
Explanation:
Localized the break, supplies a graphical trace of where the break occurs in order to detect high loss splice point as far as 25 miles.