The resistance r of a piece of wire has thermometric properties which can be described as a linear function of temperature (t), see below: where a and b are constants. the resistance of the wire is found to be 3.3 2 at the temperature of melting ice (0 °c) and 8.5 2 at the boiling of water (100 °c) at atmospheric pressure. [15 marks] a, find a and b b. determine the temperature when r is 6.9 2

Explanation:

R = a T + b ( R is linear function of T , the temperature in kelvin )

At T =  273 K , R = 3.32

Put these values in the equation above '

3.32 = 273 a + b

At 100° = 373K , R = 8.52

8.52 = 373 a + b

8.52 - 3.32 = (373 - 273 )a

a =5.2 / 100 = .052

Putting this value of a in the first equation we get the value of b as follows

3.32 = 273 x .052 + b

b = -10.876.

So equation becomes

R = .052 T - 10.876

When R = 6.92 , T =?

6.92 = .052 T -10.876

.052T = 17.796

T = 342.23K

T = 342.23 - 273 = 69.23 °C

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2