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3 years ago

You overhear two students discussing the topic of Doppler shift.

Physics

1 answer:

9966 [12]3 years ago

5 0

Answer:

agree with student 2, disagree with student 1

Explanation:

If you want to know if the wavelength of light was shifted you have to know the original wavelengths

Since we know the absorption spectrum for elements like hydrogen, we can look for these absorption lines in the star's spectra and figure out what direction these lines are shifted and tell if the star is moving away or towards us

The color of the star refers to the temperature of the star's surface which is not related to the doppler shift of the star

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A 60kg student traveling in a 1000kg car with a constant velocity has a kinetic energy of 1.2 x 10^4 J. What is the speedometer

777dan777 [17]

Answer:

17.64 km/h

Explanation:

mass of car, m = 1000 kg

Kinetic energy of car, K = 1.2 x 10^4 J

Let the speed of car is v.

Use the formula for kinetic energy.

$K = \frac{1}{2}mv^{2}$

By substituting the values

$1.2\times 10^{4} = \frac{1}{2}\times 1000\times v^{2}$

v = 4.9 m/s

Now convert metre per second into km / h

We know that

1 km = 1000 m

1 h = 3600 second

So, $v = \left (\frac{4.9}{1000} \right )\times \left ( \frac{3600}{1} \right )$

v = 17.64 km/h

Thus, the reading of speedometer is 17.64 km/h.

4 0

2 years ago

Two children who are bored while waiting for their flight at the airport decide to race from one end of the 20-m-long moving sid

QveST [7]

Answer: Phillipe wins the race

Explanation:

Given

Length of track=20 m

Velocity of Phillippe=2 m/s w.r.t sidewalk

Velocity of sidewalk=1.5 m/s

Rena velocity=2 m/s

Therefore absolute velocity of P is 2+1.5=3.5 m/s

Time taken by phillippe $\frac{20}{3.5}+\frac{20}{3.5-1.5}$

$t_P$ =5.714+10=15.714 s

Time taken by rena

$t_r=\frac{20}{2}+\frac{20}{2}=20 s$

as the time taken by phillippe is less than rena therefore Phillippe wins the race.

8 0

3 years ago

Read 2 more answers

A string vibrates at a frequency of 20Hz. what is its period?

Andreas93 [3]

We know, Period = 1/frequency = 1/20 sec.

So, your final answer is 0.05 sec

Hope this helps!

7 0

3 years ago

12)A black body is heated from 27°C to 127° C. The ratio of their energies of radiations emitted will be

Nat2105 [25]

Answer:

$81:256$ .

Explanation:

Let $T$ denote the absolute temperature of this object.

Calculate the value of $T$ before and after heating:

$T(\text{before}) = 27 + 273 = 300\; \rm K$ .

$T(\text{after}) = 127 + 273 = 400\; \rm K$ .

By the Stefan-Boltzmann Law, the energy that this object emits (over all frequencies) would be proportional to $T^4$ .

Ratio between the absolute temperature of this object before and after heating:

$\displaystyle \frac{T(\text{before})}{T(\text{after})} = \frac{3}{4}$ .

Therefore, by the Stefan-Boltzmann Law, the ratio between the energy that this object emits before and after heating would be:

$\displaystyle \left(\frac{T(\text{before})}{T(\text{after})}\right)^{4} = \left(\frac{3}{4}\right)^{4} = \frac{81}{256}$ .

4 0

2 years ago

An object with a mass 4.0 kg has a momentum of 64 kgm/s . How fast is the object traveling ?

Anastasy [175]

Answer:

The object will travel at the speed of 16 m/s.

Explanation:

Given

Mass m = 4.0 kg

Momentum p = 64 kgm/s

To determine

How fast is the object traveling?

<u>Important Tip:</u>

The product of the mass and velocity of an object — momentum.

Using the formula

$p = mv$

where

m = mass

v = velcity

p = momentum

Thus, in order to determine the speed of the object, all we need to do is to substitute p = 64 and m = 4 in the formula

$p = mv$

$64\:=\:4\times v$

switch the equation

$\:4\times \:v\:=64$

divide both sides by 4

$\frac{4v}{4}=\frac{64}{4}$

simplify

$v=16$ m/s

Therefore, the object will travel at the speed of 16 m/s.

3 0

2 years ago