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ser-zykov [4K]
2 years ago
13

A constant force of 20. newtons applied to a box causes it to move at a constant speed of 4.0 meters per second. How much work i

s done in the boxin 6.0 seconds?
1) 240 joules
2) 120 joules
3) 480 joules
4) 80. joules
Physics
1 answer:
podryga [215]2 years ago
6 0
The answer is 3) 480 joules
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What are the principles of electrodynamic​
Sveta_85 [38]

Answer:

the branch of mechanics concerned with the interaction of electric currents with magnetic fields or with other electric currents.

Explanation:

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3 years ago
Steam in a heating system flows through tubes whose outer diameter is 5 cm and whose walls are maintained at a temperature of 13
svet-max [94.6K]

Answer:

5945.27 W per meter of tube length.

Explanation:

Let's assume that:

  • Steady operations exist;
  • The heat transfer coefficient (h) is uniform over the entire fin surfaces;
  • Thermal conductivity (k) is constant;
  • Heat transfer by radiation is negligible.

First, let's calculate the heat transfer (Q) that occurs when there's no fin in the tubes. The heat will be transferred by convection, so let's use Newton's law of cooling:

Q = A*h*(Tb - T∞)

A is the area of the section of the tube,

A = π*D*L, where D is the diameter (5 cm = 0.05 m), and L is the length. The question wants the heat by length, thus, L= 1m.

A = π*0.05*1 = 0.1571 m²

Q = 0.1571*40*(130 - 25)

Q = 659.73 W

Now, when the fin is added, the heat will be transferred by the fin by convection, and between the fin and the tube by convection, thus:

Qfin = nf*Afin*h*(Tb - T∞)

Afin = 2π*(r2² - r1²) + 2π*r2*t

r2 is the outer radius of the fin (3 cm = 0.03 m), r1 is the radius difference of the fin and the tube ( 0.03 - 0.025 = 0.005 m), and t is the thickness ( 0.001 m).

Afin = 0.006 m²

Qfin = 0.97*0.006*40*(130 - 25)

Qfin = 24.44 W

The heat transferred at the space between the fin and the tube will be:

Qspace = Aspace*h*(Tb - T∞)

Aspace = π*D*S, where D is the tube diameter and S is the space between then,

Aspace = π*0.05*0.003 = 0.0005

Qspace = 0.0005*40*(130 - 25) = 1.98 W

The total heat is the sum of them multiplied by the total number of fins,

Qtotal = 250*(24.44 + 1.98) = 6605 W

So, the increase in heat is 6605 - 659.73 = 5945.27 W per meter of tube length.

5 0
3 years ago
8. What is the mass of a toy car with a speed of 12.5 m/s and 47500 J of kinetic energy?
Alla [95]

Answer:

608kg

Explanation:

Formula : <u>Kinetic</u><u> </u><u>energy</u><u> </u>

½ ×mass x speed²

<u>47500</u>

½×12.5²

=608 Kg

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3 years ago
What is peer review?...
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3 years ago
Read 2 more answers
You make a capacitor by cutting the 16.0-cm-diameter bottoms out of two aluminum pie plates, separating them by 3.25 mm, and con
dalvyx [7]

Answer:

The capacitance of your capacitor is 5.476 x 10⁻⁵ μF

Explanation:

Given;

diameter of the aluminum pie plates = 16 cm = 0.16 m

separation distance, d = 3.25 mm = 0.00325 m

voltage across the parallel plates = 6 V

C = \frac{\epsilon A}{d}

where;

C is the capacitance of your capacitor

ε is the permittivity of free space = 8.85 x 10⁻¹²  (F/m)

d is separation distance

A is the area of the plate = ¹/₄ (πd²) = 0.25 (π x 0.16²) = 0.02011 m²

C = \frac{8.85*10^{-12} *0.02011}{0.00325} = 5.476 * 10^{-11} \ F = \ 5.476 * 10^{-5} \mu F

Therefore, the capacitance of your capacitor is 5.476 x 10⁻⁵ μF

3 0
3 years ago
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