Answer:
Thus, the payback time for cavity wall insulation is 7.5 years
Answer:
The tension is 
Explanation:
From the question we are told that
The total mass is 
The radius is 
The density of air is 
Generally the upward force acting on the balloon is mathematically represented as

=> 
=> 
Here V is the volume of the spherical helium filled balloon which is mathematically represented as

=> 
=> 
So


The total momentum of the system is equal to 50 Kgm/s.
<u>Given the following data:</u>
To determine the total momentum of the system:
Mathematically, momentum is given by the formula;

<u>For Football player 1:</u>

Momentum 1 = 160 Kgm/s.
<u>For Football player 2:</u>

Momentum 1 = 210 Kgm/s.
Now, we can calculate the total momentum of the system:

Total momentum = 50 Kgm/s.
<u>Note:</u> We subtracted because the football players were moving in opposite directions.
Read more: brainly.com/question/15517471
To solve this problem we will apply the concepts related to the calculation of the speed of sound, the calculation of the Mach number and finally the calculation of the temperature at the front stagnation point. We will calculate the speed in international units as well as the temperature. With these values we will calculate the speed of the sound and the number of Mach. Finally we will calculate the temperature at the front stagnation point.
The altitude is,

And the velocity can be written as,


From the properties of standard atmosphere at altitude z = 20km temperature is



Velocity of sound at this altitude is



Then the Mach number



So front stagnation temperature



Therefore the temperature at its front stagnation point is 689.87K