<h2>
Answer: 0.17</h2>
Explanation:
The Stefan-Boltzmann law establishes that a black body (an ideal body that absorbs or emits all the radiation that incides on it) "emits thermal radiation with a total hemispheric emissive power proportional to the fourth power of its temperature":
(1)
Where:
is the energy radiated by a blackbody radiator per second, per unit area (in Watts). Knowing 
is the Stefan-Boltzmann's constant.
is the Surface area of the body
is the effective temperature of the body (its surface absolute temperature) in Kelvin.
However, there is no ideal black body (ideal radiator) although the radiation of stars like our Sun is quite close. So, in the case of this body, we will use the Stefan-Boltzmann law for real radiator bodies:
(2)
Where 
is the body's emissivity
(the value we want to find)
Isolating from (2):
(3)
Solving:
(4)
Finally:
(5) This is the body's emissivity
Newtons second law says that the acceleration of an object (produced by a net force) is directly proportional to that magnitude of the net force. E.g. F = ma
where F is the net force of an object, m is mass and a is acceleration.
For example, if an object had a large mass, there would have to be more force in order to move it than if it was lighter.
In a linear motion, if you pushed two objects, one slightly larger than the other, with the same force, the acceleration of the smaller object would be bigger than the larger one. So the motion (change in position over time), of the larger object would be seen as lesser than the smaller one (in a situation where both forces are equal).
I don't know if you still need this, but here's an answer anyways.
It was a giant cloud of matter, with negatively charged electrons inside.
1. U = Q + W
U = -500 + 1000
U = 500 J
2. The first law of thermodynamic is about the law of conservation of energy where energy in should be equal to energy out.
3. It is the windmill that does not transform energy from heat to mechanical instead it is the transforms the opposite.
4. In a heat engine, work is used to transfer thermal energy from a hot reservoir to a cold one.
5. 5.00 × 10^4 J - 2.00 × 10^4 J = 3.00 × 10^4 J
6. To increase the work done, we raise the temperature of the cold reservoir.
Answer:
The velocity of the police car is, v = 17.798 m/s
Explanation:
Given data,
The actual frequency of the siren, f = 2010 Hz
The observed frequency of siren is, f' = 2120 Hz
The velocity of the observer, v' = 0 m/s
The velocity of the source, v = ?
The formula for Doppler effect,
Where,
V - velocity of sound waves in air.
Substituting the given values,
v = 17.798 m/s
Hence, the velocity of the police car is, v = 17.798 m/s
