Answer:
a) 
b) 
c) The wall may not be under steady because the two surfaces of the wall are exposed to the air at different temperatures and they have different convective coefficient.
Explanation:
Given:
- temperature of the inner surface of the wall,

- temperature of the outer surface of the wall,

- temperature of the air outside,

- temperature of the air inside,

- coefficient of heat convection on outside,

- coefficient of heat convection on inside,

a)
The heat flux between the interior air and the wall:
The convective heat transfer rate is given as,




b)
The heat flux between the exterior air and the wall:



c)
The wall may not be under steady because the two surfaces of the wall are exposed to the air at different temperatures and they have different convective coefficient.
Answer:
huh? do you need help on math?
Explanation:
what do you mean?
Answer:
Cannonball b spends more time in the air than cannonball a.
Explanation:
Starting with the definition of acceleration, we have that:

Since both cannonballs will stop in their maximum height, their final velocity is zero. And since the acceleration in the y-axis is g, we have:

Now, this time interval is from the moment the cannonballs are launched to the moment of their maximum height, exactly the half of their time in the air. So their flying time t_f is (the minus sign is ignored since we are interested in the magnitudes only):

Then, we can see that the time the cannonballs spend in the air is proportional to the vertical component of the initial velocity. And we know that:

Finally, since
and
, we can conclude that:

In words, the cannonball b spends more time in the air than cannonball a.
Answer:
The intensity of light passing from the third polarizer is 3Io/16.
Explanation:
The law of Malus is given by

Let the incident intensity of light is Io.
The intensity of light passing from the first polarizer is

The intensity of light passing from the second polarizer is

The intensity of light passing from the third polarizer is

Answer:
3420.39 N
Explanation:
Applying,
Fd = 1/2(mv²-mu²)................. Equation 1
Where F = force on the bumber, d = distance, m = mass of the car, v = final velocity, u = initial velocity.
make F the subject of the equation
F = (mv²-mu²)/2d............... Equation 2
From the question,
Given: m = 890 kg, v = 0 m/s (to rest), u = 1.4 m/s, d = 0.255 m
Substitute these values into equation 2
F = [(890×0²)-(890×1.4²)]/(2×0.255)
F = -1744.4/0.51
F = -3420.39 N
The negative sign denotes that the force in opposite direction to the motion of the car.