Many devices have been invented to accurately measure temperature. It all started with the establishment of a temperature scale. This scale transformed the measurement of temperature into meaningful numbers.
In the early years of the eighteenth century, Gabriel Fahrenheit (1686-1736) created the Fahrenheit scale. He set the freezing point of water at 32 degrees and the boiling point at 212 degrees. These two points formed the anchors for his scale.
Later in that century, around 1743, Anders Celsius (1701-1744) invented the Celsius scale. Using the same anchor points, he determined the freezing temperature for water to be 0 degree and the boiling temperature 100 degrees. The Celsius scale is known as a Universal System Unit. It is used throughout science and in most countries.
There is a limit to how cold something can be. The Kelvin scale is designed to go to zero at this minimum temperature. The relationships between the different temperature scales are:
oK = 273.15 + oC oC = (5/9)*(oF-32) oF = (9/5)*oC+32
oF oC oK
Water boils 212 100 373
Room Temperature 72 23 296
Water Freezes 32 0 273
Absolute Zero -460 -273 0
At a temperature of Absolute Zero there is no motion and no heat. Absolute zero is where all atomic and molecular motion stops and is the lowest temperature possible. Absolute Zero occurs at 0 degrees Kelvin or -273.15 degrees Celsius or at -460 degrees Fahrenheit. All objects emit thermal energy or heat unless they have a temperature of absolute zero.
If we want to understand what temperature means on the molecular level, we should remember that temperature is the average energy of the molecules that composes a substance. The atoms and molecules in a substance do not always travel at the same speed. This means that there is a range of energy (the energy of motion) among the molecules. In a gas, for example, the molecules are traveling in random directions at a variety of speeds - some are fast and some are slow. Sometimes these molecules collide with each other. When this happens the higher speed molecule transfers some of its energy to the slower molecule causing the slower molecule to speed up and the faster molecule to slow down. If more energy is put into the system, the average speed of the molecules will increase and more thermal energy or heat will be produced. So, higher temperatures mean a substance has higher average molecular motion. We do not feel or detect a bunch of different temperatures for each molecule which has a different speed. What we measure as the temperature is always related to the average speed of the molecules in a system
Work = (500N)(15m)=7500J Power= (7500J)/(20s) =375 W
Hopefully this helps
Refraction is the change in direction of a wave, caused by the change in the wave's speed. Examples of waves include sound waves and light waves. Refraction is seen most often when a wave passes from one transparent medium to another transparent medium. Different types of medium include air and water. When a wave passes from one transparent medium to another transparent medium, the wave will change its speed and its direction. For example, when a light wave travels through air and then passes into water, the wave will slow and change direction.
There is a lot of glare off of the ice, due to the sun and it also is always good to have eye protection in case you fall face first :P
Answer:
Force (P) : Positive
Normal Force (Fn) : Zero
Weight (mg) : Zero
Kinetic Frictional Force (fk) : Negative
Explanation:
The work done by a force on an object is given by the following formula:
W = F.d
W = F d Cosθ
where,
W = Work Done
f = Force Applied
d = displacement
θ = Angle between force and displacement
<u>FOR FORCE (P)</u>:
Since, force P is parallel to the motion of the box. Therefore, θ = 0°
Hence,
W = P d Cos 0°
W = P d(1)
W = Pd
<u>Therefore, work done by force (P) is Positive.</u>
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<u>FOR NORMAL FORCE (Fn) AND WEIGHT (W)</u>:
Since, normal force and weight are perpendicular to the motion of the box. Therefore, θ = 90°
Hence,
W = Fn d Cos 90°= mg d Cos 90°
W = Fn d(0) = mg d (0)
W = 0
<u>Therefore, work done by Normal Force (Fn) and Weight (mg) is Zero.</u>
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<u>FOR KINETIC FRICTIONAL FORCE (fk)</u>:
Since, kinetic frictional force acts in the opposite direction of motion of the box. Therefore, θ = 180°
Hence,
W = fk d Cos 180°
W = fk d(-1)
W = -fk d
<u>Therefore, work done by Kinetic Frictional Force (fk) is Negative.</u>
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