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3 years ago

Which of these statements best describes a similarity between the two galaxies?

2 answers:

8 0

Elliptical and Spiral have some similarities, they both are huge and contain lost of dust and also they are held by gravitational forces.

olasank [31]3 years ago

3 0

<u>Answer:</u> The correct statement is both are held together by gravitational forces.

<u>Explanation:</u>

Galaxies are defined as the system which contain millions or billions of stars bind together by gas or dust and held together by gravitational forces.

There are three types of galaxies: elliptical, spiral and irregular shaped. All the galaxies have different shapes of centers. Some may have elongated centers, some can shape like bars.

The galaxies do not change their shape from time to time. Minor changes might be seen but change is shape does not happen.

Hence, the correct statement is both are held together by gravitational forces.

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A cord is used to vertically lower an initially stationary block of mass M = 3.6 kg at a constant downward acceleration of g/7.

dalvyx [7]

Answer:

(a) $W_c=127.008 J$

(b) $W_g=148.176 J$

(c) K.E. = 21.168 J

(d) $v=3.4293m.s^{-1}$

Explanation:

Given:

mass of a block, M = 3.6 kg

initial velocity of the block, $u=0 m.s^{-1}$

constant downward acceleration, $a_d= \frac{g}{7}$

$\Rightarrow$ That a constant upward acceleration of $\frac{6g}{7}$ is applied in the presence of gravity.

∴ $a=- \frac{6g}{7}$

height through which the block falls, d = 4.2 m

(a)

Force by the cord on the block,

$F_c= M\times a$

$F_c=3.6\times (-6)\times\frac{9.8}{7}$

$F_c=-30.24 N$

∴Work by the cord on the block,

$W_c= F_c\times d$

$W_c= -30.24\times 4.2$

We take -ve sign because the direction of force and the displacement are opposite to each other.

$W_c=-127.008 J$

(b)

Force on the block due to gravity:

$F_g= M.g$

∵the gravity is naturally a constant and we cannot change it

$F_g=3.6\times 9.8$

$F_g=35.28 N$

∴Work by the gravity on the block,

$W_g=F_g\times d$

$W_g=35.28\times 4.2$

$W_g=148.176 J$

(c)

Kinetic energy of the block will be equal to the net work done i.e. sum of the two works.

mathematically:

$K.E.= W_g+W_c$

$K.E.=148.176-127.008$

K.E. = 21.168 J

(d)

From the equation of motion:

$v^2=u^2+2a_d\times d$

putting the respective values:

$v=\sqrt{0^2+2\times \frac{9.8}{7}\times 4.2 }$

$v=3.4293m.s^{-1}$ is the speed when the block has fallen 4.2 meters.

6 0

3 years ago

A wave has a wavelength of 4.9 m and a velocity of 9.8 m/s. The medium through which this wave is traveling is then heated so th

garri49 [273]

Answer:

the wavelength is 9.8 meters

Explanation:

We can use the relationship:

Velocity = wavelenght*frequency.

Initially we have:

wavelenght = 4.9m

velocity = 9.8m/s

then:

9.8m/s = 4.9m*f

f = 9.8m/s/4.9m = 2*1/s

now, if the velocity is doubled and the frequency remains the same, we have:

2*9.8m/s = wavelenght*2*1/s

wavelenght = (2*9.8m/s)*(1/2)s = 9.8 m

6 0

3 years ago

Read 2 more answers

A vertical wire carries current in the upward direction. an electron is traveling parallel to the wire. what is the angle α betw

Luden [163]

Angle α between the velocity of theelectron and the magnetic field of the wire will be 90 degree

7 0

3 years ago

What is the magnitude of the electric force between a proton and an electron when they are at a distance of 4.09 angstrom from e

Zinaida [17]

Answer:

$F=1.38*10^{-9}N$

Explanation:

According to Coulomb's law, the magnitude of the electric force between two point charges is directly proportional to the product of the magnitude of both charges and inversely proportional to the square of the distance that separates them:

$F=\frac{kq_1q_2}{d^2}$