Answer:
No temperature change occurs from heat transfer if ice melts and becomes liquid water (i.e., during a phase change). For example, consider water dripping from icicles melting on a roof warmed by the Sun. Conversely, water freezes in an ice tray cooled by lower-temperature surroundings.
Explanation:
Energy is required to melt a solid because the cohesive bonds between the molecules in the solid must be broken apart such that, in the liquid, the molecules can move around at comparable kinetic energies; thus, there is no rise in temperature. Similarly, energy is needed to vaporize a liquid, because molecules in a liquid interact with each other via attractive forces. There is no temperature change until a phase change is complete. The temperature of a cup of soda initially at 0ºC stays at 0ºC until all the ice has melted. Conversely, energy is released during freezing and condensation, usually in the form of thermal energy. Work is done by cohesive forces when molecules are brought together. The corresponding energy must be given off (dissipated) to allow them to stay together Figure 2.
The energy involved in a phase change depends on two major factors: the number and strength of bonds or force pairs. The number of bonds is proportional to the number of molecules and thus to the mass of the sample. The strength of forces depends on the type of molecules. The heat Q required to change the phase of a sample of mass m is given by
Q = mLf (melting/freezing,
Q = mLv (vaporization/condensation),
where the latent heat of fusion, Lf, and latent heat of vaporization, Lv, are material constants that are determined experimentally.
<h2>Question</h2>
why freezer is made in the upper part of refrigrator
<h2>✒ Answer</h2>
the cold air produced from it is denser than the warmer air in the bottom
<h3>Explaination</h3>
Freezer is normally provided at the top of the refrigerator, because density of the cold air is high compared to the hot air. In a refrigerator the air contacts with the cooling coil and gets cooling.Because of the high density the cold air gets down and the warm air/hot air moves upward and gets cooling from the cooling coil/evaporator coil. This process is repeated. If the Freezer is provided at the bottom place of the refrigerator, the cold air can't to move full area of the refrigerator. So the freezer is normally provided at the top at the refrigerator
Answer: Input work is the work done on a machine as the input force acts through the input distance.Other ways it would be the work done on a body or system, that is, forces that are applied to the body or system. This is in contrast to output work which is a force that is applied by the body or system to something else.Output work is the work done by a machine as the output force acts through the output distance. The machine does to the object to increase the output distance.
Explanation:
Answer: They travel equal distances
Explanation:
Distance is amount of space covered from one point to another. It is measured in metres. Distance = speed x time taken
In this case,
- Since Tony and Tanya both run at the same speed: let speed = b
- Also, both run for the same amount of time: let time = c
Therefore, distance covered by Tony and Tanya = speed x time taken
Distance = b x c
Distance = bc (i.e Tony travelled a distance of bc, so also Tanya)
Answer:
v = 1.98*10^8 m/s
Explanation:
Given:
- Rod at rest in S' frame
- makes an angle Q = sin^-1 (3/5) in reference frame S'
- makes an angle of 45 degree in frame S
Find:
What must be the value of v if as measured in S the rod is at a 45 degree)
Solution:
- In reference frame S'
x' component = L*cos(Q)
y' component = L*sin(Q)
- Apply length contraction to convert projected S' frame lengths to S frame:
x component = L*cos(Q) / γ (Length contraction)
y component = L*sin(Q) (No motion)
- If the rod is at angle 45° to the x axis, as measured in F, then the x and y components must be equal:
L*sin(Q) = L*cos(Q) / γ
Given: γ = c / sqrt(c^2 - v^2)
c / sqrt(c^2 - v^2) = cot(Q)
1 - (v/c)^2 = tan(Q)
v = c*sqrt( 1 - tan^2 (Q))
For the case when Q = sin^-1 (3/5)::
tan(Q) = 3/4
v = c*sqrt( 1 - (3/4)^2)
v = c*sqrt(7) / 4 = 1.98*10^8 m/s
