<u>Answer:</u>
Things become hot and cold because of the transfer of energy.
<u>Explanation:</u>
The energy possessed by an object or system is called thermal energy and heat is the flow of this energy. While the law of conversation of energy states that energy is not destroyed or created, it just transfers from one object to another.
When a hot object is placed in normal conditions, it transfers heat to the environment until both are at the same temperature and heat transfers from the environment to the cold objects placed in normal conditions.
The magnitude (in N) of the force she must exert on the wrench is 150.1 N.
<h3>
Force exerted by the wrench</h3>
The force exerted by the wrench is calculated using torque formula as follows;
torque, τ = F x r x sinθ
where;
- F is the applied force
- r is the perpendicular distance if force applied
F = τ /(r sinθ)
F = (39) / (0.3 sin 60)
F = 150.1 N
Thus, the magnitude (in N) of the force she must exert on the wrench is 150.1 N.
Learn more about torque here: brainly.com/question/14839816
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Answer:

Explanation:
Refractive Index: It is a measure to find how fast the light travels through a medium. It is ration of the speed of light in vacuum to speed of light in the medium. Speed of light is not constant and varies depending on the density of the medium.
In vacuum the speed of light is 300000 km/s and is denoted by c. When the light beam enters any medium the speed will decrease. Here it is given that the speed in plastic is v. Thus the refractive index(n) is given as:

It is a dimensionless no.
Theories have both an explanatory an a predictive function. True
Just carbon is a metalloid not oxygen