<h2>
Answers:</h2>
-The first direct detection of gravitational waves came in 2015
-The existence of gravitational waves is predicted by Einstein's general theory of relativity
-Gravitational waves carry energy away from their sources of emission
<h2>
Explanation:</h2>
Gravitational waves were discovered (theoretically) by Albert Einstein in 1916 and "observed" for the first time in direct form in 2015 (although the results were published in 2016).
These gravitational waves are fluctuations or disturbances of space-time produced by a massive accelerated body, modifying the distances and the dimensions of objects in an imperceptible way.
In this context, an excellent example is the system of two neutron stars that orbit high speeds, producing a deformation that propagates like a wave,<u> in the same way as when a stone is thrown into the water</u>. So, in this sense, gravitational waves carry energy away from their sources
.
Therefore, the correct options are D, E and F.
Answer:
80Ω
Explanation:
Resistance in a series circuit (when one resistor is after another in the same line) is calculated with the following equation
Total resistance = R1 + R2 + R3...Rn
Substitute in your values and solve for total resistance
Total resistance = 60 + 20 = 80Ω
The force required is 319 N
Explanation:
The force of static friction is a force that acts an object on a surface, when this object is pushed by another force to put it in motion. The direction of the force of friction is opposite to the direction of the force of push, and its value increases as the force of push increases, up to a maximum value given by:

where
is the coefficient of friction
W is the weight of the object
Therefore, in order to put the object in motion, the force applied must be greater than this value.
For the pile of leaves in this problem, we have:
(coefficient of friction)
(weight of the leaves)
Substituting, we find:

Learn more about force of friction:
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