<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
Answer:
1.05m or 105cm
Explanation:
Using the hooke's law equation as follows;
F = –k.x
Where;
F = force (N)
x = extension length (m)
k = constant of proportionality (N/m)
According to the information given in this question;
Displacement (x) = 85cm = 85/100 = 0.85m
Force = 12500N
Using F = kx, we find the proportionality constant
k = F/x
K = 12500/0.85
K = 14705.8N/m.
Also, since K = 14705.8N/m, the displacement (x), when the force increases to 15500N is;
F = kx
x = F/k
x = 15500/14705.8
x = 1.05m or 105cm
Answer:
Work done by the frictional force is 
Explanation:
It is given that,
Mass of the car, m = 1000 kg
Initial velocity of car, u = 26.1 m/s
Finally, it comes to rest, v = 0
We have to find the work done by the frictional forces. Work done is equal to the change in kinetic energy as per work - energy theorem i.e.
W = −340605 J
or
Hence, the correct option is (a).
Answer:
2.6 m
Explanation:
The work done by the bird is given by
where
F is the force exerted
d is the distance covered
In this problem, we know:
is the work
is the force
Solving the equation for d, we find the distance covered by the bird:
