Answer:
The climate of the earth throughout history has always been <em><u>fluctuated between hot and cold periods. </u></em>
Answer:
Charge, 
and it is negative.
Explanation:
Given that,
Mass of the charge, 
Electric field, E = 640 N/C
To find,
Charge
Solution,
The electric force and the force of gravity are balanced in the electric field. It is given by :
Since, the electric field is in downward direction. The force must be upward direction s that the charge is negative.
The correct option is D.
Resonance is a phenomenon in which a vibrating system or an external force induces another system to vibrate at greater amplitude at particular frequencies.
When a tuning fork is struck with another object, the tuning fork will start to vibrate as a result of the force that is exerted by the object used to struck it. This type of vibration, without direct excitation by a man is an example of resonance.
Answer: True
Explanation:
It should be noted that when refrigerant is added in vapor form to the operating refrigeration system, then the addition of the refrigerant should be to the low-pressure side of the refrigeration system.
Furthermore, when system pressures are lower than the pressure in the refrigerant tank as stated in the question, then the refrigerant can be added to both the high and low pressure sides of the system.
Therefore, the correct option is true.
