Answer:
The reason is because both are exposed to a virtually infinite heat sink, due to the virtually infinite mass and of the surrounding environment, compared to the sizes of either the cup or the kettle such that the equilibrium temperature, 
reached is the same for both the cup and the kettle as given by the relation;
Due to the large heat sink, T₂ - T₁ ≈ 0 such that the temperature of the kettle and that of the cup will both cool to the temperature of the environment
Explanation:
The correct answer is - a. was a sign of danger.
Once the people saw that the ocean waters are receding and were living vast space without water behind them, they knew that something big and very dangerous will happen. And in fact it did. The water that was sucked in in the place were there was a crack on the ocean floor, got shot back under big pressure and it had very big speed, as well as having waves that were destroying anything on their way.
Answer:
Friction:-
The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. There are at least two types of friction force - sliding and static friction. Though it is not always the case, the friction force often opposes the motion of an object. For example, if a book slides across the surface of a desk, then the desk exerts a friction force in the opposite direction of its motion. Friction results from the two surfaces being pressed together closely, causing inter molecular attractive forces between molecules of different surfaces. As such, friction depends upon the nature of the two surfaces and upon the degree to which they are pressed together. The maximum amount of friction force that a surface can exert upon an
EG:-
A coaster sliding against a table.
Gravity:-
The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth. The force of gravity on earth is always equal to the weight of the object as found
EG:-
The force that causes a car to coast downhill even when you aren't stepping on the gas.
Elastic:-
Elasticity is the ability of a material to return to its original shape after being stretched or compressed. When an elastic material is stretched or compressed, it exerts elastic force. This force increases the more the material is stretched or compressed.
EG:-
An archer's stretched bow
Answer:
The source of all wave motion is a disturbance in matter or a vibration
