The motion of a projectile is described in a coordinate system (up and North are positive). At a particular instant, the magnitude of the horizontal
component of the velocity is 5 m/s and the magnitude of the vertical
component of the velocity is - 8 m/s. Which is most correct about the
object?
The projectile is at its maximum height
O the projectile is ascending (going up)
the projectile is descending (going down)
the projectile has hit the ground
the projectile has just been launched above the horizontally

The emissivity of the radiation shield is    

Explanation:

From the question we are told that

   The temperature of the first parallel plate is  

    The temperature of the second  parallel plate is  

    The  emissivity of first plate is  

    The  emissivity of first plate is  

Generally the total radiation heat that is been transferred without the shield is mathematically represented as

Where   is the Stefan-Boltzmann constant which has a value  

Substituting values

From the question we are told the that using the radiation shield would reduce the radiation heat transfer by 15%

  So the new heat transfer is

 So    

Now this new radiation heat transfer can be mathematically represented as  

   Where the emissivity of the  radiation shield and n is the number of radiation shield

Substituting values