PLEASE HELP!!

Hydrogen bonding is a strong attractive force. T OR F

vodomira [7]

Answer:

F

Hope it helps you!

6 0

3 years ago

If we compare the force of gravity too strong nuclear force we would conclude that

Yuri [45]

The force of gravity is much weaker than the strong nuclear force. But the strong nuclear force only acts over short distances, such as within the nuclues. The gravitational force can act over infinite distance.

6 0

4 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

If a truck is heading south at a velocity of 90m/s for 10 seconds how far did it travel?

RoseWind [281]

Answer:

Truck will be at a distance of 720 m

Explanation:

Speed of the truck is given as 90 m/sec

Time for which truck travel t = 10 seconds

We have to find the distance that how much truck travel in 8 sec with speed of 90 m/sec

We know that distance is given by $distance=velocity\times time$

So distance traveled by truck in 8 sec will be equal to $=90\times 8 =720m$

So truck will be at a distance of 720 m

3 0

4 years ago

A mass of 3 slugs (this is the English unit of mass, a pound is a force) is attached to a vertical spring with a spring constant

motikmotik

Answer:

equation of motion for the mass is x(t) = e^αt ( C1 cos √{α² - ω²} t + C2 sin √{α² - ω²} t )

Explanation:

Given data

mass = 3 slugs = 3 * 32.14 = 96.52 lbs

constant k = 9 lbs/ft

Beta = 6lbs * s/ft

mass is pulled = 1 ft below

to find out

equation of motion for the mass

solution

we know that The mass is pulled 1 ft below so

we will apply here differential equation of free motion i.e

dx²/dt² + 2 α dx/dt + ω² x =0 ........................1

here 2 α = Beta / mass

so 2 α = 6 / 96.52

α = 0.031

α² = 0.000961 ...............2

and

ω² = k/mass

ω² = 9 /96.52

ω² = 0.093 ..................3

we can say that from equation 2 and 3 that α² - ω² = -0.092239

this is less than zero

so differential equation is

x(t) = e^αt ( C1 cos √{α² - ω²} t + C2 sin √{α² - ω²} t )

equation of motion for the mass is x(t) = e^αt ( C1 cos √{α² - ω²} t + C2 sin √{α² - ω²} t )

3 0

3 years ago