Emissivityis a measure of how much thermal radiation a body emits to its environment. On the other hand we have that reflectivity is a measure of how much is reflected, and transmissivity is a measure of how much passes through the object. If a body is required to be ideally reflective to its maximum efficiency, the body should NOT have the property of transmissivity or emissivity. Therefore it should be 0 its emittivity.
Correct answer would be A : ZERO.
The answer is to this question D
Answer:
15m/s
Explanation:
add the two speeds and divide by 2
10+20=30
30/2=15
Answer:
<em>0.97c</em>
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Explanation:
From the relativistic equation for length contraction, we have
= 
where
is the final length of the object
is the original length of the object before contraction
β = 
where v is the speed of the object
c is the speed of light in free space = 3 x 10^8 m/s
The equation can be re-written as
/ = 
For the length to contract to one-fourth of the proper length, then
/ = 1/4
substituting into the equation, we'll have
1/4 =
substituting for β, we'll have
1/4 = 
squaring both side of the equation, we'll have
1/16 = 1 - 
= 1 - 1/16
= 15/16
square root both sides of the equation, we have
v/c = 0.968
v = <em>0.97c</em>
Answer:
3600joules
Explanation:
formula :W=FS
W=work done (J)
F=force (N)
S=displacement moved in the direction of force (m)
200N×18m
=3600J
