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3 years ago

Match the simple machine with the correct definition.

1 answer:

3 0

A. any slanting, flat surface is an inclinded plane

B. a rigid bar that rotates about a pivot called a fulcrum is a lever

C. an inclined plane wrapped around a cylinder is a screw

D. load is in the middle of a second class lever

E. two inclined planes placed back to back form a wedge

F. a wheel turning around an axle inserted through its center
is cleverly labeled a "wheel and axle".

G. effort is in the middle of a third class lever

H. a circular lever that consists of a grooved wheel rotating
about a hub is a pulley

I. fulcrum is between the effort and load of a first class lever

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With the intensity at about half of maximum, how does the current change when you increase the frequency of the light?

PIT_PIT [208]

Answer:

Increase

Explanation:

Energy of given as follows

E = h f

Where f is the frequency of incident light

when high frequency light falls then it will increase the number of produce photon and that increase in number of photon will lead to increase in the number of electron.When number of electron will increase it mean that current will also increase.

So we can say that when frequency increase then current will increase.

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3 years ago

Clarissa has a credit card with a limit of $1,000 and pays her balance in full each month. If Clarissa needs a short-term loan,

Aloiza [94]

Answer:

B.she cannot use it because the credit card is not collareral

Explanation:

sorry if am wrong

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3 years ago

Runner 1 has a velocity of 10 m/s west. Runner 2 has a velocity of 7 m/s east. From the frame of reference of runner 2, what is

Vsevolod [243]

Answer:

17 m/s west

Explanation:

Runner 1 has velocity = 10 m/s west

runner 2 has velocity = 7 m/s east

From the frame of reference of runner 2, we can imagine runner 2 as standing still, and runner 1 moving away from him, towards the west with their combined velocity of

velocity = 10 m/s + 7 m/s = 17 m/s west

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3 years ago

What is a likely consequence of preventing prescribed burns to forest ecosystems?

sattari [20]

Your answer is A. Natural wildfires will burn longer and hotter when they occur because there is more underbrush and fuel available.

3 0

3 years ago

Read 2 more answers

Expectant mothers many times see their unborn child for the first time during an ultrasonic examination. In ultrasonic imaging,

Rzqust [24]

A) A. 380 kHz

To clerly see the image of the fetus, the wavelength of the ultrasound must be 1/4 of the size of the fetus, therefore

$\lambda=\frac{1}{4}(1.6 cm)=0.4 cm=0.004 m$

The frequency of a wave is given by

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

where

v is the speed of the wave

$\lambda$ is the wavelength

For the ultrasound wave in this problem, we have

v = 1500 m/s is the wave speed

$\lambda=0.004 m$ is the wavelength

So, the frequency is

$f=\frac{1500 m/s}{0.004 m}=3.75\cdot 10^5 Hz=375 kHz \sim 380 kHz$

B) B. f(c+v)/c−v

The formula for the Doppler effect is:

$f'=\frac{v\pm v_r}{v\pm v_s}f$

where

f' is the apparent frequency

v is the speed of the wave

$v_r$ is the velocity of the receiver (positive if the receiver is moving towards the source, negative if it is moving away from the source)

$v_s$ is the speed of the source (positive if the source is moving away from the receiver, negative if it is moving towards the receiver)

f is the original frequency

In this problem, we have two situations:

- at first, the ultrasound waves reach the blood cells (the receiver) which are moving towards the source with speed

$v_r = +v$ (positive)

- then, the reflected waves is "emitted" by the blood cells (the source) which are moving towards the source with speed

$v_s = -v$

also

v = c = speed of sound in the blood

So the formula becomes

$f'=\frac{c + v}{v - v_s}f$

C. A. The gel has a density similar to that of skin, so very little of the incident ultrasonic wave is lost by reflection

The reflection coefficient is

$R=\frac{(Z_1 -Z_2)^2}{(Z_1+Z_2)^2}$

where Z1 and Z2 are the acoustic impedances of the two mediums, and R represents the fraction of the wave that is reflected back. The acoustic impedance Z is directly proportional to the density of the medium, $\rho$ .

In order for the ultrasound to pass through the skin, Z1 and Z2 must be as close as possible: therefore, a gel with density similar to that of skin is applied, in order to make the two acoustic impedances Z1 and Z2 as close as possible, so that R becomes close to zero.

3 0

3 years ago