Eva is in a closed, dark room. She uses her arm muscles to turn on a lamp. When she moves her hand closer to the lamp, the light heats her hand. The light bounces off the pages of a book and into her eyes.If this room is a closed system, what happens to the total amount of energy in the room?
A.
It remains constant.
B.
It decreases.
C.
It increases, then decreases.
D.
It increases.
Answers
Well, we know that the total energy in a closed system remains constant.
The problem with the story of Eva is that she is not in a closed system.
If the dark room were really a closed system, then she could press the
button or turn the switch all day, and the lamp could not light. It needs
electrical energy coming in from somewhere in order to turn on.
Let's say that Eva used her arm muscles to strike a match and light the
candle on the table. Then we would have have food energy, muscle
energy, chemical energy in the match, chemical energy in the candle,
heat and light energy coming out of the candle, heat energy soaking into
her hand, light energy bouncing off of the book and into her eyes ... all
going on during the story, and the sum total of all of them would remain
constant.
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Answer:
The time the ball it takes to have the downward speed 4 m/s is 1.22 sec.
Explanation:
Lets explain the motion of the ball
The ball is kicked straight upwards with an initial vertical speed of 8.0 m/s
Its velocity decreases util it reaches the maximum height
At the maximum height its velocity is equal to zero
Then it fall down to the ground
We can ignore air resistance
Lets find the time it takes the ball to reach the maximum height
The acceleration of gravity is -9.8 m/s²
The initial velocity is 8 m/s upward
The final velocity is zero
So lets use the rule v = u + gt, where v is the final velocity, u is the initial
velocity, g is the acceleration of gravity and t is the time
u = 8 , v = 0 , g = -9.8
Substitute these value in the equation above
0 = 8 - 9.8 t
Add 9.8 t for both sides
9.8 t = 8
Divide both sides by 9.8
t = 40/49 seconds
The ball falls withe initial velocity zero and increases to reach 4 m/s
The velocity 4 m/s is downward
The acceleration of gravity is 9.8 m/s²
By using the same rule
u = 0 , v = 4 , g = 9.8
4 = 0 + 9.8 t
4 = 9.8 t
Divide both sides by 9.8
t = 20/49
The time the ball it takes to have the downward speed 4 m/s is the sum
of the two times above
The time the ball it takes = seconds
The time the ball it takes to have the downward speed 4 m/s is 1.22 sec.
Answers
The answer is D traits may be determined by multiple genes!! :) glad to help
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the answer would be A. the number and arrangement of the electrons in an atom
ik bc i took the test
:)
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The light waves reflecting off a red stop sign longer than the waves reflecting off a Violet colored jacket.
The visible spectrum is composed of seven wavelengths. These wavelengths are red, orange, yellow, green, blue, indigo, violet. The wavelengths of these waves decrease in this order.
This means that the wavelength of red light is longer than the wavelength of violet light therefore the light waves reflecting off a red stop sign longer than the waves reflecting off a Violet colored jacket.
Learn more: brainly.com/question/14281129
Answers
Sliding friction - the friction that occurs upon a moving object; it is always lower than the static friction of the same object.
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