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3 years ago

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The Solar System is made up of eight planets, numerous comets, asteroids, and moons, and the Sun. The force that holds all of th

ese objects together is _______. A. tension B. gravity C. electromagnetic attraction D. magnetism

2 answers:

Nastasia [14]3 years ago

7 0

Answer:

B. GRAVITY is the answer

ollegr [7]3 years ago

7 0

Answer:

<em>The answer is B. gravity </em>

Explanation:

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Which of these is a concave lens?

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Answer:

I think its last one picture

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3 years ago

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A speed truck locks it’s brakes and it skids to a stop. If the truck’s total mass were doubled, it’s skidding distance would be?

Gnom [1K]

Answer:

The skidding distance would be doubled

Explanation:

When the truck applies the brakes and slows down, its motion is a uniformly accelerated motion, so its skidding distance can be found by using the suvat equation

$v^2-u^2=2as$

where

v = 0 is the final velocity (zero since the truck comes to a stop)

u is the initial velocity

a is the acceleration

s is the skidding distance

The acceleration can also be written as

$a=\frac{F}{m}$

where F is the force applied by the brakes and m the mass of the truck. Substituting into the previous equation,

$-u^2 = 2\frac{F}{m}s\\s = -\frac{mu^2}{2F}$

We see that the skidding distance is proportional to the mass: therefore, if the mass of the truck is doubled, the skidding distance will double as well.

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3 years ago

yKpoI14uk [10]

Answer:

Option C. Rate of change of velocity

Explanation:

To know the correct answer to the question, it is important we know the definition of power.

Power can be defined as the rate at which work is done. Mathematically, it is expressed as:

Power = work / time

Work and energy has the same unit of measurement i.e joule. Thus, power can also be defined as the rate at which energy is transferred i.e

Power = enery / time

Energy is measured in Joules and time in second. Thus, power can also be defined as amount of joules transfered per second.

Power = Joule / sec

The rate of change of velocity on the other hand is termed acceleration.

Thus, the answer to the question is option C.

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3 years ago

Water evaporating from a pond does so as if it were diffusing across an air film 0.15 cm thick. The diffusion coefficient of wat

QveST [7]

Answer:

The water level will drop by about 1.24 cm in 1 day.

Explanation:

Here Mass flux of water vapour is given as

$j_{H_2O}=\frac{D}{l} \bigtriangleup c$

where

$j_{H_2O}$ is the mass flux of the water which is to be calculated.

D is diffusion coefficient which is given as $0.25 cm^2/s$

l is the thickness of the film which is 0.15 cm thick.
$\bigtriangleup c$ is given as

$\bigtriangleup c= \frac{P_{sat}-P_a}{RT}$

In this

$P_{sat}$ is the saturated water pressure, which is look up from the saturated water property at 20°C and 0.5 saturation given as 2.34 Pa

$P_a$ is the air pressure which is given as 0.5 times of $P_{sat}$

R is the universal gas constant as $8.314 kJ/kmol-K$

T is the temperature in Kelvin scale which is $20+273= 293K$

By substituting values in the equation

$\bigtriangleup c= \frac{P_{sat}-P_a}{RT} \\ \bigtriangleup c= \frac{P_{sat}-0.5P_{sat}}{RT} \\ \bigtriangleup c= \frac{0.5P_{sat}}{RT} \\ \bigtriangleup c= \frac{0.5 \times 2.34}{8.314 \times 293} \\\bigtriangleup c= 0.48 mol/m^3$

Converting $\bigtriangleup c$ into $cm^3/cm^3$

As 1 mole of water 18 $cm^3$ so

$\bigtriangleup c= 0.48 mol/m^3 \\ \bigtriangleup c= 0.48 \times 18 \times 10^{-6} cm^3/cm^3 \\ \bigtriangleup c= 8.64 \times 10^{-6} cm^3/cm^3$

Putting this in the equation of mass flux equation gives

$j_{H_2O}=\frac{D}{l} \bigtriangleup c \\ j_{H_2O}=\frac{0.25}{0.15} \times 8.64 \times 10^{-6} \\ j_{H_2O}=14.4 \times 10^{-6} cm/s$

For calculation of water level drop in a day, converting mass flux as

$j_{H_2O}=14.4 \times 10^{-6} \times 24 \times 3600 cm/day\\ j_{H_2O}=1.24 cm/day$

So the water level will drop by about 1.24 cm in 1 day.

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3 years ago

What happens to the Total Energy as the spring bounce?

fiasKO [112]

Total energy will remain the same

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