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-Dominant- [34]
4 years ago
13

Determine which heat transfers below are due to the process of conduction. I) You walk barefoot on the hot street and it burns y

our toes. II) When you get into a car with hot black leather in the middle of the summer and your skin starts to get burned. III) A flame heats the air inside a hot air balloon and the balloon rises. IV) A boy sits to the side of a campfire. He is 10 feet away, but still feels warm. A) I and II B) III and IV C) I, II, and IV D) II, III, and IV
Physics
2 answers:
Rudik [331]4 years ago
3 0

I) You walk barefoot on the hot street and it burns your toes.

The road is in direct contact with your skin. Thermal energy from the road will transfer to the bottom of your feet, then to the rest of your body. This is an example of conduction.


II) When you get into a car with hot black leather in the middle of the summer and your skin starts to get burned.

Just like in the previous example, the hot leather is in direct contact with your skin (I guess if you're going to drive naked). Thermal energy from the leather will transfe to your skin, then to the rest of your body. This is also conduction.


III) A flame heats the air inside a hot air balloon and the balloon rises.

The flame heats air directly at the bottom of the balloon. The warm air expands and becomes less dense. This will rise and let the unheated, denser air in the balloon fall down toward the flame. This is an example of the convection cycle.


IV) A boy sits to the side of a campfire. He is 10 feet away, but still feels warm.

The campfire heats air directly nearby. The warm air expands and moves away from the fire in all directions, leaving behind unheated, denser air to be heated up. Some of the warm air reaches the boy. This is another example of convection.


The answer is A) 1 and 2.

Shkiper50 [21]4 years ago
3 0

Explanation:the correct answer is A

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A wire of radius 5 x 10⁻⁴ m is needed to prepare a coil of resistance 40 Ω. The resistivity of the material of the wire is 3.14x
SIZIF [17.4K]

Answer:

100 m

Explanation:

From the question,

R = Lρ/A.................... Equation 1

Where R = resistance of the wire, L = length of the wire, ρ = resistivity of the wire, A = cross sectional area of the wire.

But,

A = πr².................... Equation 2

Where r = radius of the wire.

Substitute equation 2 into equation 1

R = Lρ/πr²

Make L the subject of the equation

L = Rπr²/ρ...................... Equation 3

Given: R = 40 Ω, r = 5×10⁻⁴ m, ρ = 3.14×10⁻⁷ Ωm

Constant: π = 3.14

Substitute these values into equation 3

L = [40×3.14×( 5×10⁻⁴)²]/ (3.14×10⁻⁷)

L = 40×3.14×25×10⁻⁸/(3.14×10⁻⁷)

L = 100 m

Hence the length of the wire is 100 m

4 0
3 years ago
HELP PLEASE
denis-greek [22]
B) Distance: the farther, the weaker!
4 0
4 years ago
Read 2 more answers
What is the entropy change associated with the expansion of one mole of an ideal gas from an initial volume of v to a final volu
Kaylis [27]

Answer:

ΔS = 7.618 J/K

Explanation:

The entropy change associated to an isothermal process is:

ΔS = \frac{Q}{T}

We can calculate Q (heat) how:

Q = nRTln(\frac{Vf}{Vi})

   Where Vf = 2.5v

               Vi = v

               R = 8.314J/mol.k  (Constant of ideal gases)

               n: Number of moles = 1 mol

Then

Q = nRTln(2.5)

ΔS = \frac{nRTln(2.5)}{T}

ΔS = (1)(8.314)ln(2.5)

ΔS = 7.618 J/K

4 0
3 years ago
Consider the case in which the clay is launched along Path Y. The sphere of clay is launched with an initial velocity of v0 and
Helen [10]

Answer:

    w = \frac{m}{ml^2 + I R^2 }  v l

Explanation:

Let's form a system formed by the clay sphere and the rod, in this case the angular momentum is conserved

initial instant. Before the crash

          L₀ = m v l

Final moment. After the collision with the clay stuck to the rod

          L_f = I_{total} w

angular momentum is conserved

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the total moment of inertia is the sum of the moments of inertia of the two bodies

the moment of inertia of the rod is

        I_rod = I R²

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we substitute

          w = \frac{m}{ml^2 + I R^2 }  v l

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