Answer: 33.35 minutes
Explanation:
A(t) = A(o) *(.5)^[t/(t1/2)]....equ1
Where
A(t) = geiger count after time t = 100
A(o) = initial geiger count = 400
(t1/2) = the half life of decay
t = time between geiger count = 66.7 minutes
Sub into equ 1
100=400(.5)^[66.7/(t1/2)
Equ becomes
.25= (.5)^[66.7/(t1/2)]
Take log of both sides
Log 0.25 = [66.7/(t1/2)] * log 0.5
66.7/(t1/2) = 2
(t1/2) = (66.7/2 ) = 33.35 minutes
Answer:

Explanation:
Given that

We know that
Rex=ρvx/μ
So


All other quantities are constant only x is a variable in the above equation .so lets take all other quantities as a constant C

We also know that
Nux=hx/K

m is the constant

This is local heat transfer coefficient
The average value of h given as


---------1
The value of local heat transfer coefficient at x=L

-----------2
From 1 and 2 we can say that

Answer:
The engine consists of a fixed cylinder and a moving piston. The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the power-train, this motion drives the vehicle's wheels.
Explanation:
Answer:
b)Poly crystalline and amorphous materials with small diameter
Explanation:
Fibers have high length to diameter ratio and also have high strength.Generally length of fibers is very high and diameter is very low as compare to length.
Mostly fibers is used to transfer data from one place to another place with help of fiber optical cables.Fiber optic cables is used in telecommunication.In these cables data covert in to the electric single and reach at define location and after data is decode and covert from electric single in to original data.
Fibers poly crystalline and amorphous materials with small diameter.
Of course they are needed because without them the society wouldn’t be as nice as it is right now and plus there would be no more buildings ! :)