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4 years ago

3. Pedro threw a penny into a fountain and it sank to the bottom. Which of the following would explain

Physics

2 answers:

solong [7]4 years ago

4 0

Answer:

Explanation:

A is not correct as there is much more water then penny meaning the water has more mass. The same can be said about C as the water also has more volume. Answer D is incorrect as the temperature of the penny is irrelevant to its ability to sink. That leaves us with option B, which is true as the penny is composed of metal allowing it to sink in the water due to having more density.

____ [38]4 years ago

3 0

Answer:

its B because we're not talking about mass even tho most people would have chosen A cuz it says mass and u they would think its apart of density but if ur testing to see density ur figuring out which object will sink and which one will float so da reason why da penny snuck it cuz da density is greater den da water and copper has a better chance of sinking den floating so dats why its B I hope dis helps :3

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A carpenter builds an exterior house wall with a layer of wood 3.0 cm thick on the outside and a layer of Styrofoam insulation 2

Leno4ka [110]

Answer:

A. T=15.54 °C

B. Q/A= 0.119 W/m2

Explanation:

To solve this problem we need to use the Fourier's law for thermal conduction:

$Q= kA\frac{dT}{dx}$

Here, the rate of flow per square meter must be the same through the complete wall. Therefore, we can use it to find the temperature at the plane where the wood meets the Styrofoam as follows:

$\frac{Q}{A} =\frac{T_1-T_0}{d_w}k_w=\frac{T_2-T_1}{d_s}k_s\\T_1(\frac{k_w}{d_w}+\frac{k_s}{d_s})=T_2\frac{k_s}{d_s}+T_0\frac{k_w}{d_w}\\T_1=\frac{T_2\frac{k_s}{d_s}+T_0\frac{k_w}{d_w}}{\frac{k_w}{d_w}+\frac{k_s}{d_s}}\\T_1= 15.54 \°C$

Then, to find the rate of heat flow per square meter, we have:

$\frac{Q}{A}=\frac{T_1-T_0}{d_w}k_w=0.119 \frac{W}{m^2}\\\frac{Q}{A}=\frac{T_2-T_1}{d_s}k_s= 0.119 \frac{W}{m^2}$

$T_0: Temperature \ in \ the \ house\\T_1: Temperature \ at \ the \ plane \ between \ wood \ and \ styrofoam\\T_2: Temperature \ outside\\k_w: k \ for \ wood\\d_w: wood \ thickness\\k_s: k \ for \ styrofoam\\d_s: styrofoam \ thickness$

7 0

3 years ago

Vector A= 3.7 i + 1.0 j and vector B = 3.0 i + 6.5 j. What is vector<br> (A-B).A?

kicyunya [14]

Answer:

(A - B).A = -2.91

Explanation:

First, let's define the sum and dot product of vectors.

For two vectors V = (x₁, y₁) and W = (x₂, y₂) we have:

sum (or subtraction):

V + W = (x₁, y₁) + (x₂, y₂) = (x₁ + x₂, y₁ + y₂)

dot product:

V.W = (x₁, y₁).(x₂, y₂) = x₁*x₂ + y₁*y₂

Here remember the notation:

V = x₁*i + y₁*j = (x₁, y₁)

Now let's solve our problem, we have:

A = (3.7, 1.0)

B = (3.0, 6.5)

Then:

(A - B).A = ( (3.7, 1.0) - (3.0, 6.5) ).(3.7, 1.0)

= (3.7 - 3.0, 1.0 - 6.5).(3.7, 1.0)

= (0.7, -5.5).(3.7, 1.0) = (0.7*3.7) + (-5.5)*(1.0) = -2.91

8 0

3 years ago

A car accelerates from 20.0 m/s to 28.0 m/s over a distance of 50.0 m. What is the car’s acceleration?

Blababa [14]

Answer:

Explanation:

$V^2=V^2_o+2a(x_f-x_i)$

$28^2=20^2+2a(50)\\784=400+100a\\384=100a\\a=3.84m/s^2$

5 0

3 years ago

A pipe originally has a radius of 1.25m. It narrows down to a radius of 0.55m. If the original force in the big pipe is 72N, wha

Gemiola [76]

Use direct proportionality: If 1.25 m = 72 N, then 0.55 m = y

0.55 m × 72 = 39.6.

39.6÷1,25 gives you your answer which is 31.68 N.

5 0

3 years ago

Compare and contrast the strength of the forces between two objects with a mass of 1 kg each, a charge of 10

DochEvi [55]

Answer:

Let's see the similarities between the two forces

* are proportional to the product of a magnitude, mass or charge

* They are inversely proportional to the square of the distance

* They are long-range forces since zero is not made up to an infinite distance. The gravitational force is always attractive, the electrical force can be attractive or repulsive.

The differences in them

* The electric force in much greater than the gravitational force

* The gravitational force is always attractive, the electrical force can be attractive or repulsive.

Explanation:

Let's start by calculating each force.

Gravitational force

F = $G \frac{m_1m_2}{r^2}$

let's calculate

F = 6.67 10⁻¹¹ 1 1 / 1²

F = 6.67 10⁻¹¹ N

Electric force

F = $k \frac{q_1q_2}{r^2}$

indicates that the charge is q = 10 C

F = 9 10⁹ 10 10 / 1²

F = 9 10¹¹ N

Let's see the similarities between the two forces

* are proportional to the product of a magnitude, mass or charge

* They are inversely proportional to the square of the distance

* They are long-range forces since zero is not made up to an infinite distance. The gravitational force is always attractive, the electrical force can be attractive or repulsive.

The differences in them

* The electric force in much greater than the gravitational force

* The gravitational force is always attractive, the electrical force can be attractive or repulsive.

3 0

3 years ago