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4 years ago

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a 40-kg mass rest at the edge of a board that is 2 meters long. the coefficients of friction are .80 and .40. the board is slowl

y raised until the mass just begins to slide. at what angle does the mass begin to slide?

1 answer:

DanielleElmas [232]4 years ago

3 0

At about 38.6598 degrees
see attachment for work

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What do miles, kilometers, and light-years have in common?<br><br>

Radda [10]

They are all units of measure of length

Explanation:

Length is a scalar quantity representing a distance between two points, and it can be expressed in different units.

The SI units of the length is the metre (m), which is defined as the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second.

A unit which is common used is a multiple of the meter, the kilometre (km) which corresponds to 1000 metres:

1 km = 1000 m

Another unit used in the UK system is the mile (mi), where the conversion factor between miles and metres is

1 mi = 1609.34 m

Finally, these units are not suitable to be used to measure astronomical distances - such as those between stars and galaxies. For this, another unit is used, which is the light-year (ly), which corresponds to the distance travelled by the light in a vacuum in one year, and its conversion factor to the metre is:

$1 ly = 9.46\cdot 10^{15}ly$

Learn more about distance here:

brainly.com/question/3969582

#LearnwithBrainly

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3 years ago

Radar uses radio waves of a wavelength of 2.4 \({\rm m}\) . The time interval for one radiation pulse is 100 times larger than t

blondinia [14]

Answer:

120 m

Explanation:

Given:

wavelength 'λ' = 2.4m

pulse width 'τ'= 100T ('T' is the time of one oscillation)

The below inequality express the range of distances to an object that radar can detect

τc/2 < x < Tc/2 ---->eq(1)

Where, τc/2 is the shortest distance

First we'll calculate Frequency 'f' in order to determine time of one oscillation 'T'

f = c/λ (c= speed of light i.e 3 x $10^{8}$ m/s)

f= 3 x $10^{8}$ / 2.4

f=1.25 x $10^{8}$ hz.

As, T= 1/f

time of one oscillation T= 1/1.25 x $10^{8}$

T= 8 x $10^{-9}$ s

It was given that pulse width 'τ'= 100T

τ= 100 x 8 x $10^{-9}$ => 800 x $10^{-9}$ s

From eq(1), we can conclude that the shortest distance to an object that this radar can detect:

$x_{min}$ = τc/2 => (800 x $10^{-9}$ x 3 x $10^{8}$ )/2

$x_{min}$ =120m

8 0

4 years ago

In 1958, Meselson and Stahl conducted an experiment to determine which of the three proposed methods of DNA replication was corr

Korolek [52]

Answer:

Explanation:

The original has hybrid 15N/14N DNA, and the second generation has both hybrid 15N/14N DNA and 14N/14N DNA. No 15N/15N DNA was observed. In this experiment:

Nitrogen is a significant component of DNA. 14N is the most bounteous isotope of nitrogen, however, DNA with the heavier yet non-radioactive and 15N isotope is likewise practical.

E. coli was developed for several generations in a medium containing NH4Cl with 15N. When DNA is extracted from these cells and centrifuged on a salt density gradient, the DNA separates at which its density equals to the salt arrangement. The DNA of the cells developed in 15N medium had a higher density than cells developed in typical 14N medium. After that, E. coli cells with just 15N in their DNA were transferred to a 14N medium.

DNA was removed and compared to pure 14N DNA and 15N DNA. Immediately after only one replication, the DNA was found to have an intermediate density. Since conservative replication would result in equal measures of DNA of the higher and lower densities yet no DNA of an intermediate density, conservative replication was eliminated. Moreso, this result was consistent with both semi-conservative and dispersive replication. Semi conservative replication would result in double-stranded DNA with one strand of 15N DNA, and one of 14N DNA, while dispersive replication would result in double-stranded DNA with the two strands having mixtures of 15N and 14N DNA, either of which would have appeared as DNA of an intermediate density.

The DNA from cells after two replications had been completed and found to comprise of equal measures of DNA with two different densities, one corresponding to the intermediate density of DNA of cells developed for just a single division in 14N medium, the other corresponding to DNA from cells developed completely in 14N medium. This was inconsistent with dispersive replication, which would have resulted in a single density, lower than the intermediate density of the one-generation cells, yet at the same time higher than cells become distinctly in 14N DNA medium, as the first 15N DNA would have been part evenly among all DNA strands. The result was steady with the semi-conservative replication hypothesis. The semi conservative hypothesis calculates that each molecule after replication will contain one old and one new strand. The dispersive model suggests that each strand of each new molecule will possess a mixture of old and new DNA.

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4 years ago

A rocket burns fuel at a rate of 199 kg/s and exhausts the gas at a relative speed of 9 km/s. Find the thrust of the rocket. Ans

andreyandreev [35.5K]

Answer:

1.791 MN

Explanation:

Thrust of the rocket can be found using the relation

T = v.dm/dt, where

T = thrust off the rocket

v = speed of the rocket, 9 km/s = 9000 m/s

dm/dt = rate at which fuel burns, 199 kg/s

Substituting the values into the formula, we have

T = 9000 * 199

T = 1791000 N

T = 1.791*10^6 N

Since 1 MN = 10^6, thus

T = 1.791 MN

7 0

3 years ago

In his experiments on "cathode rays" during which he discovered the electron, J.J. Thomson showed that the same beam deflections

Andrews [41]

Answer:

A) his observation is of little importance ,

B) This observation is very important since the movement of the point of light depends on the relationship between the already magnetic electric force

C) see that in this second case it is 4 times less

D) the force of gravity is of the order of 10⁻⁴⁰

therefore it is 10²⁸ times less than the electric force,

Explanation:

A) This observation is of little importance since the cacodylate ray tube always emits electrons, regardless of the material of which it is made.

B) This observation is very important since the movement of the point of light depends on the relationship between the already magnetic electric force

C) the elect's load is 1.6 10⁻¹⁹ C its mass is 9.1 10⁻³¹ kg, let's look for its relation

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look for this in the case of an atom, let's use the lightest atom hydrogen

the homogenize have an electron of charge 1.6 10⁻¹⁹ C

and a mass of 1.6735575 10⁻²⁷ ka

e / M = 1.6 10⁻⁻¹⁹ / 1.67 10⁻²⁷

e / M = 0.96 10⁸ N

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8 0

3 years ago