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3 years ago

10

Evan notices a small fire in his workplace. Since the fire is small and the atmosphere is not smoky he decides to fight the fire

himself. What’s the one thing Evan didn’t consider?

1 answer:

Norma-Jean [14]3 years ago

7 0

Answer:

not calling the firemean

Explanation:

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At a festival, spherical balloons with a radius of 140.cm are to be inflated with hot air and released. The air at the festival

Tpy6a [65]

Answer:

find attached

Explanation:

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3 years ago

If you know that the change in entropy of a cup of coffee where heat was added is 20 J/K, and that the temperature of the coffee

Anna35 [415]

Answer:

5000J

Explanation:

Given in the question that

Heat added to the coffee cup is, ΔS = 20 J/K

The temperature of the coffee, T = 250 K

Now, using the formula for the entropy change

$\bigtriangleup S=-\frac{\bigtriangleup H}{T}$ ...........(1)

Where,

ΔS is the entropy change

ΔH is the enthalpy change

T is the temperature of the system

substituting the values in the equation (1)

we get

$20=-\frac{\bigtriangleup H}{250}$

ΔH=250×20

ΔH=5000 J

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3 years ago

Please read and answer each question carefully.

Klio2033 [76]

the answer is (c)

After the vehicle is involved in a car accident or fire

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4 years ago

(a) The room-temperature electrical conductivity of a semiconductor specimen is 13 (Ω-m)-1. The hole concentration is known to b

Aleksandr-060686 [28]

Answer: a) 0.24E+20 m-3. b) p-type extrinsic.

Explanation:

The current density in a semiconductor is composed by two types of charge carriers: electrons and holes.

This parameter, is proportional to the Electric field within the semiconductor, being the proportionality constant, the electrical conductivity of the material, that takes into account the charge carrier concentrations, and the mobility for each type.

The expression for electrical conductivity is as follows:

σ = q . ne . µe + q . np . µp

Replacing by the given values, and the value of q (charge of an electron), we can get the only unknown that remains, ne , as follows:

ne =( σ – (q . np . µp)) / q µe = (13 (Ω.m)-1 – (1.6E-19) coul(4.0E+20) m-3.0.18) m2/V-s /( (1.6E-19).0.38) coul.m2/V-s

ne = 0.24E+20.

As ne is smaller than np, this means that the semiconductor behaves like a p-type extrinsic one.

7 0

3 years ago

Two steel plates of 15 mm thickness each are clamped together with an M14 x 2 hexagonal head bolt, a nut, and one 14R metric pla

Blababa [14]

Answer:

a) 50 mm

b) 808.24 MN/m

Explanation:

Given:

Thickness of each steel plate = 15mm

a) To find suitable length of bolt, we'll use:

Length of bolt = grip length + height of nut

To find the grip length since there is a washer, we'll use:

Grip length = plate thickness + washer thickness

Since we have 2 plates of 15mm thickness,

Plate thickness = 15 + 15 = 30mm

Using the table, a metric plain washer has a thickness of 3.5mm

Grip length = 30 + 3.5 =33.5 mm

Height of nut: Using table A-31, height of hexagonal nut is 12.8 mm

Therefore,

Length of bolt = 33.5 + 12.8 = 46.3

Rounde up to the nearest 5mm, we'll get 50mm

Length of bolt = 50mm

b) Bolt stiffness:

Threaded length for L ≤ 125mm

LT = 2*d + 6

Where d = 14mm, from table(8-7)

= 2*14 + 6

= 34 mm

Area of unthreaded portion:

Ad= $\frac{\pi}{4} d^2 = \frac{pi}{4} * 14^2 = 153.94 mm^2$

Length of unthreaded portion in grip:

Ld = 50 - 34 = 16mm

Length of threaded portion in grip:

Lt = 33.5 - 16 = 17.5mm

Bolt stiffness = $\frac{A_d A_t E}{A_d l_t + A_t l_d}$

$= \frac{153.94 * 115 * 207}{(153.94*17.5)+(115*16)} = 808.24$

Bolt stiffness = 808.24 MN/m

7 0

3 years ago