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3 years ago

How do scientists use the Doppler effect to understand the universe?

2 answers:

6 0

There's a very subtle thing going on here, one that could blow your mind.

Wherever we look in the universe, no matter what direction we look,
we see the light from distant galaxies arriving at our telescopes with
longer wavelengths than the light SHOULD have.

The only way we know of right now that can cause light waves to get
longer after they leave the source is motion of the source away from
the observer. The lengthening of the waves on account of that motion
is called the Doppler effect. (The answer to the question is choice-c.)

But that may not be the only way that light waves can get stretched. It's
the only way we know of so far, and so we say that the distant galaxies
are all moving away from us.

From that, we say the whole universe is expanding, and that right there is
one of the strongest observations that we explain with the Big Bang theory
of creation.

Now: If ... say tomorrow ... a competent Physicist discovers another way
for light waves to get stretched after they leave the source, then the whole
"expanding universe" idea is out the window, and probably the Big Bang
theory along with it !

Now that our mind has been blown, come back down to Earth with me,
and I'll give you something else to think about:

It's true that when we look at distant galaxies, we do see their light
arriving in our telescopes with longer wavelengths than it should have.
And then we use the Doppler effect to calculate how fast that galaxy
is moving away from us. That's all true. Astronomers are doing it
every day. I mean every night.

So here's the question for you to think about ... maybe even READ about:

When the light from a distant galaxy pours into our telescope, and we
look at it, and we measure its wavelength, and we find that the wavelength
is longer than it should be ... how do we know what it should be ? ? ?

djverab [1.8K]3 years ago

3 0

Answer: The correct option is (c).

Explanation:

In Doppler effect, there is an apparent change in the frequency when there is a relative motion between the source and the observer or the source or the listener.

When the source and the observer are approaching each other then there is increase in the frequency.

When the source and the observer are moving away from each other then there is decrease in the frequency.

Therefore, Scientists use the Doppler effect to understand the universe to determine motion of object.

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An athlete at the gym holds a 3.0 kg steel ball in his hand. His arm is 60 cm long and has a mass of 3.8 kg, with the center of

Serggg [28]

Answer:

(a) τ = 26.58 Nm

(b) τ = 18.79 Nm

Explanation:

(a)

First we find the torque due to the ball in hand:

τ₁ = F₁d₁

where,

τ₁ = Torque due to ball in hand = ?

F₁ = Force due to ball in hand = m₁g = (3 kg)(9.8 m/s²) = 29.4 N

d₁ = perpendicular distance between ball and shoulder = 60 cm = 0.6 m

τ₁ = (29.4 N)(0.6 m)

τ₁ = 17.64 Nm

Now, we calculate the torque due to the his arm:

τ₁ = F₁d₁

where,

τ₂ = Torque due to arm = ?

F₂ = Force due to arm = m₂g = (3.8 kg)(9.8 m/s²) = 37.24 N

d₂ = perpendicular distance between center of mass and shoulder = 40% of 60 cm = (0.4)(60 cm) = 24 cm = 0.24 m

τ₂ = (37.24 N)(0.24 m)

τ₂ = 8.94 Nm

Since, both torques have same direction. Therefore, total torque will be:

τ = τ₁ + τ₂

τ = 17.64 Nm + 8.94 Nm

τ = 26.58 Nm

(b)

Now, the arm is at 45° below horizontal line.

First we find the torque due to the ball in hand:

τ₁ = F₁d₁

where,

τ₁ = Torque due to ball in hand = ?

F₁ = Force due to ball in hand = m₁g = (3 kg)(9.8 m/s²) = 29.4 N

42.42 cm = 0.4242 m

τ₁ = (29.4 N)(0.4242 m)

τ₁ = 12.47 Nm

Now, we calculate the torque due to the his arm:

τ₁ = F₁d₁

where,

τ₂ = Torque due to arm = ?

F₂ = Force due to arm = m₂g = (3.8 kg)(9.8 m/s²) = 37.24 N

d₂ = perpendicular distance between center of mass and shoulder = 40% of (60 cm)(Cos 45°) = (0.4)(42.42 cm) = 16.96 cm = 0.1696 m

τ₂ = (37.24 N)(0.1696 m)

τ₂ = 6.32 Nm

Since, both torques have same direction. Therefore, total torque will be:

τ = τ₁ + τ₂

τ = 12.47 Nm + 6.32 Nm

τ = 18.79 Nm

3 0

2 years ago

Why does a box on the seat of a car slide around on the c one the car speeds up slows down or turns a corner?

Feliz [49]

Because the box keeps going straight at the same speed, while the seat under it speeds up, slows down, or changes direction.

8 0

2 years ago

Based on this electric field diagram, which statement best compares the charge of A with B?

lilavasa [31]

Based on this electric field diagram, the statement which best compares the charge of A with B is "A is negatively charged and B is positively charged. The charge on A is greater than that on B".

Answer: Option A

Explanation:

The charge is quantized represented as elementary charge, about 1.602×10−19 coulombs. Their are two kinds of electric charging: positive and negative (usually transported, separately, by protons and electrons). Like charges repel each other, while attraction occurs among unlike charges. An entity without net charge is considered neutral. If a piece of matter comprises more electrons than protons, it has a negative charge, when there are fewer, it'll have a positive charge and when there are equal amounts, this will be neutral.

4 0

3 years ago

Before Freddy lands on the skateboard it has a certain momentum. After landing, the skateboards momentum

Nadya [2.5K]

Answer:

remains the same

Explanation:

Momentum refers to the quantity of motion of a body. When any body of mass moves, it possess momentum. Numerically,

Momentum = mass x velocity

i.e. momentum is the product of the mass x velocity

Momentum of a body is always conserved.

In the context, the skateboard has certain momentum before Freddy lands on it. After Freddy lands, the momentum of skateboard remains the same, there is no change in the momentum.

This is because, here the momentum is conserved. After Freddy lands on the skateboard, the total mass on the skateboard increases and so the velocity decreases making the momentum same before the landing.

3 0

2 years ago

5. Each of five satellites makes a circular orbit about an object that is much more massive than any of the satellites. The mass

Vikentia [17]

The options of the question are missing. I have attached it.

Answer:

Satellite in option B will have the greatest speed.

Explanation:

From kepplers third law, we know that

V² = GM/R

Thus, v = √(GM/R)

Where;

v is velocity

G is gravitational constant

M is mass

R is radius

Looking at the options, let's start from the first one;

Option A

Here, mass = (1/2)m and radius = R

So, v = √(GM/R) thus v = √(G(m/2)/R) = √(Gm/2R)

Option B

Here, mass = m and radius = (1/2)R

Thus v = √(Gm/(R/2)) = √(2Gm/R)

Option C

Here, mass = m and radius = R

Thus v = √(Gm/R)

Option D

Here, mass = m and radius = 2R

Thus v = √(Gm/(2R))

Now, inspecting all the options, it's clear that option B will have the greatest velocity because it's numerator is the biggest and will in turn lead to higher velocity.

4 0

3 years ago