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Vadim26 [7]
3 years ago
11

If a burning log is a black object with a surface area of 0.25 m2 and a temperature of 800 8c, how much power does it emit as th

ermal radiation?
Physics
1 answer:
tresset_1 [31]3 years ago
8 0

The correct answer of this question: 18789.79 watt.

EXPLANATION:

As per the question, the surface area of the log is given as A = 0.25\ m^2

The temperature of the of the surface of the log t = 800 ^0C

We know that t^0C\ =(273+t)\ K

                      ⇒ 800 degree celsius= 800+273 K

                                                           = 1073 K.

Here, K stands for kelvin scale.

We are asked to calculate the thermal power radiation .

The power is defined as the amount of energy released per unit time.

Hence, power is calculated as-

                                Power P = \sigma AT^4

                                               = 5.67\times 10^{-8} \times 0.25\times (1073)^4\ watt

                                               = 18789.79 watt.      [ans]

Here, \sigma is the Stefan-Boltzmann constant and T is the absolute temperature of the log.

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All endothermic reactions absorb heat and make the surroundings warm
svet-max [94.6K]

Answer:

b: false

Explanation:

It's true that endothermic reactions absorb heat from their surrounding.  But this makes the surroundings cooler, not warmer.

6 0
3 years ago
the mass of a brick is 4 kg, find the mass of water displaced by it when completely immersed in water.​
vova2212 [387]

Answer:

The correct answer is = 1.6

Explanation:

Density of water = 1000kg/m³ = d₁

Mass of brick = 4kg = m

Density of brick = 2.5 g/cm³ = 2.5 × 1000 =2500 kg/m³ = d₂

Volume of brick = m/d₂ = 4/2500 =16/10000 = 0.0016 L = v

Buoyant Force = v × d₁ × g          (g= acceleration due to gravity =9.8m/s²)

= 0.0016 × 1000 × 9.8 = 15.68 Newtons

By the Archimedes' Principle, the buoyant force is equal to the weight of the liquid displaced by an object.

Weight of the water displaced=Buoyant Force

=Mass of water displaced × g,

as weight = mass × acceleration due to gravity

15.68= mass of brick × 9.8

15.68/9.8 =Mass of water displaced

1.6 kg = Mass of water displaced

4 0
3 years ago
How does the frequency of infrared electromagnetic waves compare with the frequency of radio and microwaves?
iVinArrow [24]

Answer:

Answer is B.

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8 0
2 years ago
a 5.0 kg ball is dropped from a 2.5 m high window. what is the velocity of the ball just before it hits the ground?
julsineya [31]

Answer:

Approximately 7.0\; \rm m \cdot s^{-1}.

Assumption: the ball dropped with no initial velocity, and that the air resistance on this ball is negligible.

Explanation:

Assume the air resistance on the ball is negligible. Because of gravity, the ball should accelerate downwards at a constant g = 9.81 \; \rm m \cdot s^{-2} near the surface of the earth.

For an object that is accelerating constantly,

v^2 - u^2 = 2\, a \, x,

where

  • u is the initial velocity of the object,
  • v is the final velocity of the object.
  • a is its acceleration, and
  • x is its displacement.

In this case, x is the same as the change in the ball's height: x = 2.5\; \rm m. By assumption, this ball was dropped with no initial velocity. As a result, u = 0. Since the ball is accelerating due to gravity, a = 9.81\; \rm m \cdot s^{-2}.

v^2 - u^2 = 2\, g \cdot h.

In this case, v would be the velocity of the ball just before it hits the ground. Solve for

v^2 = 2\, a\, x + u^2.

\begin{aligned}v &= \sqrt{2\, a\, x + u^2} \\ &= \sqrt{2\times 9.81 \times 2.5 + 0} \\ &\approx 7.0\; \rm m\cdot s^{-1}\end{aligned}.

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Two separate magnets.
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