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2 years ago

8

The formula for calculating power is work divided by time (power = work ÷ time). What are two ways of stating the same relations

hip?

2 answers:

UNO [17]2 years ago

7 0

If F is constant one could rewrite the equations like this also:

$P = \frac{W}{t} = \frac{F s}{t} = Fv$

nirvana33 [79]2 years ago

4 0

I think they just want you to rewrite it two other ways:

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2 years ago

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In very cold weather, a significant mechanism for heat loss by the human body is energy expended in warming the air taken into t

Pie

Answer:

A) $Q_a=74256\ J$

B) $Q=93562560\ J$

Explanation:

Given:

temperature of air, $T_a=-19+273=254\ K$

temperature of lungs, $T_l=37+273=310\ K$

specific Heat exchanged from the lungs , $c_l=0.47\ J.kg^{-1}.K^{-1}$

specific heat of air, $c_a=1020\ J.kg^{-1}.K^{-1}$

mass of 1 L air, $m'=1.3\ kg$

breath rate, $b=21\ breath.min^{-1}$

A)

Now,

amount of heat needed to warm the air of lungs to the body temperature:

$Q_a=m'.c_a.\Delta T$

$Q_a=1.3\times1020\times (310-254)$

$Q_a=74256\ J$

B)

Amount of heat lost per hour:

<u>No. of breaths per hour:</u>

$B=b.60$

$B=21\times 60$

$B=1260$

<u>Now the total loss of energy in 1 hr.:</u>

$Q=Q_a.B$

$Q=74256\times 1260$

$Q=93562560\ J$

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2 years ago

A wave is a disturbance that transmits energy from one location to another without transmitting matter with it.

GenaCL600 [577]

I think it’s true!!!

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2 years ago

According to a rule-of-thumb. every five seconds between a lightning flash and the following thunder gives the distance to the f

Bond [772]

Answer:

$S_{s}=300 m/s$

The rule for kilometers is that every three seconds between a lightning flash and the following thunder gives the distance to the flash in kilometers.

Explanation:

In order to use the rule of thumb to find the speed of sound in meters per second, we need to use some conversion ratios. We know there is 1 mile per every 5 seconds after the lightning is seen. We also know that there are 5280ft in 1 mile and we also know that there are 0.3048m in 1ft. This is enough information to solve this problem. We set our conversion ratios like this:

$\frac{1mi}{5s}*\frac{5280ft}{1mi}*\frac{0.3048m}{1ft}=321.87m/s$

notice how the ratios were written in such a way that the units got cancelled when calculating them. Notice that in one ratio the miles were on the numerator of the fraction while on the other they were on the denominator, which allows us to cancel them. The same happened with the feet.

The problem asks us to express the answer to one significant figure so the speed of sound rounds to 300m/s.

For the second part of the problem we need to use conversions again. This time we will write our ratios backwards and take into account that there are 1000m to 1 km, so we get:

$\frac{5s}{1mi}*\frac{1mi}{5280ft}*\frac{1ft}{0.3048m}*\frac{1000m}{1km}=3.11s/km$

This means that for every 3.11s there will be a distance of 1km from the place where the lightning stroke. Since this is a rule of thumb, we round to the nearest integer for the calculations to be made easily, so the rule goes like this:

The rule for kilometers is that every three seconds between a lightning flash and the following thunder gives the distance to the flash in kilometers.

3 0

2 years ago