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2 years ago

If the sign of work is negative,

Physics

1 answer:

aivan3 [116]2 years ago

5 0

If the sign of work is negative, that means the force and the motion are in opposite directions.

Let's say you see something roll off of the shelf. You catch it, and you let it down slowly and gently.

Gravity exerted down-force on it and it moved down. Gravity did positive work on it.

YOU exerted UP-force on it and it moved down. YOU did negative work on it.

(Also, the falling object exerted down-force on your hand, and your hand moved down. The falling object did positive work on your hand ! Where did THAT energy come from ? It came from the potential energy that the object had while it was on the shelf. Your hand absorbed that energy on the way down, doing negative work. So the object didn't have any kinetic energy when it reached the floor, and it did NOT splinter the floor or shatter in smithereens. It had barely enough energy left to make a sound when it hit the floor.)

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A sample of glass has a mass of 15 g and takes up 14.3 cm 3 of space. What is the density? If you drop a piece of the same glass

mr Goodwill [35]

The density will be 1.05
The mass will be 13.65

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3 years ago

Which one of the following statements concerning the Stefan-Boltzmann equation is correct? The equation can be used to calculate

Helen [10]

"The equation can be used to calculate the power absorbed by any surface" statement concerning the Stefan-Boltzmann equation is correct.

Answer: Option A

<u>Explanation:</u>

According to Stefan Boltzmann equation, the power radiated by black body radiation source is directly proportionate to the fourth power of temperature of the source. So the radiation transferred is absorbed by another surface and that absorbed power will also be equal to the fourth power of the temperature. So the equation describes the relation of net radiation loss with the change in temperature from hotter temperature to cooler temperature surface.

$P=e \sigma A\left(T^{4}-T_{c}^{4}\right)$

So this law is application for calculating power absorbed by any surface.

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2 years ago

The siren on an ambulance emits a sound of frequency 2.80×103Hz. If the ambulance is traveling at 26.0 m/s (93.6 km/h or 58.2 mi

Norma-Jean [14]

To solve this problem it is necessary to apply the concepts related to the described wavelength through frequency and speed. Mathematically it can be expressed as:

$\lambda = \frac{v}{f}$

Where,

$\lambda =$ Wavelength

f = Frequency

v = Velocity

Our values are given as,

$f = 2.8*10^3Hz$

$v = 340m/s \rightarrow$ Speed of sound

Keep in mind that we do not use the travel speed of the ambulance because we are in front of it. In case it approached or moved away we should use the concepts related to the Doppler effect:

Replacing we have,

$\lambda = \frac{340}{2.8*10^3}$

$\lambda = 0.1214m$

Therefore the frequency that you hear if you are standing in from of the ambulance is 0.1214m

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2 years ago

A container of gas molecules is at a pressure of 2 atm and has amass density of 1.7 grams per liter. All of the molecules in the

Tpy6a [65]

Answer:

The speed of nitrogen molecule is 1.87 m/s.

Explanation:

Given that,

Pressure = 2 atm

Density = 1.7 grams/liter

Atomic weight = 28 grams

We need to calculate the temperature

Using formula of idea gas

$PV=nRT$

$P=\dfrac{WRT}{VM}$

$P=\dfrac{\rho RT}{M}$

$T=\dfrac{PM}{\rho R}$

Put the value into the formula

$T=\dfrac{2\times28}{1.7\times0.0821}$

$T=401.2\ K$

We need to calculate the speed of nitrogen molecule

Using formula of RMS speed

$V_{rms}=\sqrt{\dfrac{3RT}{M}}$

$V_{rms}=\sqrt{\dfrac{3\times0.0821\times401.2}{28}}$

$V_{rms}=1.87\ m/s$

Hence, The speed of nitrogen molecule is 1.87 m/s.

5 0

3 years ago

What is newton's third law second law first law ?

sergeinik [125]

Answer:

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8 0

2 years ago

Read 2 more answers