A boulder is raised above the ground, so that its potential energy relative to the ground is 200 J. Then it is dropped. Estimate
1 answer:
Answer:
200 J
Explanation:
In this problem, I assume there is no air resistance, so the system is isolated (=no external forces).
For an isolated system, the total mechanical energy is constant, and it is given by:
where
KE is the kinetic energy
PE is the potential energy
The kinetic energy is the energy due to the motion of the object, while the potential energy is the energy due to the position of the object relative to the ground.
At the beginning, when the boulder is raised above the ground, its height above the ground is maximum, while its speed is zero; it means that all its mechanical energy is just potential energy, and it is:
As the boulder falls down, its altitude decreases, so its potential energy decreases, while the speed increases, and the kinetic energy increases. Therefore, potential energy is converted into kinetic energy.
Eventually, just before the boulder hits the ground, the height of the object is zero, and the speed is maximum; this means that all the energy has now converted into kinetic energy, and we have
Therefore, the kinetic energy just before hitting the ground is 200 J.
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<u>Answer:</u> The change in entropy of the given process is 1324.8 J/K
<u>Explanation:</u>
The processes involved in the given problem are:
Pressure is taken as constant.
To calculate the entropy change for same phase at different temperature, we use the equation:
.......(1)
where,
= Entropy change
= specific heat capacity of medium
m = mass of ice = 0.15 kg = 150 g (Conversion factor: 1 kg = 1000 g)
= final temperature
= initial temperature
To calculate the entropy change for different phase at same temperature, we use the equation:
.......(2)
where,
= Entropy change
m = mass of ice
= enthalpy of fusion of vaporization
T = temperature of the system
Calculating the entropy change for each process:
- <u>For process 1:</u>
We are given:
Putting values in equation 1, we get:
- <u>For process 2:</u>
We are given:
Putting values in equation 2, we get:
- <u>For process 3:</u>
We are given:
Putting values in equation 1, we get:
- <u>For process 4:</u>
We are given:
Putting values in equation 2, we get:
- <u>For process 5:</u>
We are given:
Putting values in equation 1, we get:
Total entropy change for the process =
Total entropy change for the process =
Hence, the change in entropy of the given process is 1324.8 J/K
Answer
given,
angle between two polarizing filters = 45°
filter reduce intensity = ?
a) I = I₀ Cos² θ
here θ = 45⁰
intensity of the light is reduced by 0.500
correct answer from the given option D
b) direction of the polarization
θ = 45°
Answer:
True
Explanation:
Pressure is defined as:
where
F is the magnitude of the force perpendicular to the surface
A is the surface
Therefore, pressure is inversely proportional to the area of the surface:
this means that, assuming that the forces in the two situations (which have same magnitude) are both applied perpendicular to the surface, the force exerted over the smaller area will exert a greater pressure. Hence, the statement"
<em>"A force acting over a large area will exert less pressure per square inch than the same force acting over a smaller area"</em>
is true.