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tino4ka555 [31]
3 years ago
13

An alert physics student stands beside the tracks as a train rolls slowly past. He notes that the frequency of the train whistle

is 452 Hz when the train is approaching him and 442 Hz when the train is receding from him. Using these frequencies, he calculates the speed of the train. What value does he find
Physics
1 answer:
Dovator [93]3 years ago
4 0

Answer:The velocity of the train is 3.84m/s

Explanation:

According to the Doppler effect, if the source is moving towards you then the apparent frequency of the sound emitted by the source is higher and if the source is moving away from you then the apparent frequency of the sound emitted by the source is smaller.

This is given by:

fo = V +-Vo/ V +-Vo × source

Where fo= observed frequency

V= velocity of sound

Vo= vo it of the observer

fsource= frequency the source

Given:

Observed frequency of the approaching train fo1= 452Hz

The observed frequency of train= fo2= 442Hz

Velocity of sound= 334m/s

Velocity of source=?

Train approaching the observer is given by:

fo1= V/(V - Vs)× source ...eq1

Train passes the student is given by:

fo2= V/(V - Vs)×source ...eq2

Divide eq1 by eq2

452/442 = (343+Vs)/(343 - Vs)

1.02 =(343+Vs)/(343 -Vs)

Cross multiply

1.02(343- Vs) = 343 + Vs

350.76 - 1.02Vs = 343 + Vs

Collecting like terms

350.76 -343= 1.02Vs+ Vs

7.76 = 2.02Vs

Vs= 7.76/2.02

Vs= 3.84m/s

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An object is swung in a horizontal circle on a length of string that is 0.93 m long. Its acceleration is 26.36 m/s2. What is the
Igoryamba

Answer:

The object takes approximately 1.180 seconds to complete one horizontal circle.  

Explanation:

From statement we know that the object is experimenting an Uniform Circular Motion, in which acceleration (a), measured in meters per square second, is entirely centripetal and is expressed as:

a = \frac{4\pi^{2}\cdot R}{T^{2}} (1)

Where:

T - Period of rotation, measured in seconds.

R - Radius of rotation, measured in meters.

If we know that a = 26.36\,\frac{m}{s^{2}} and R = 0.93\,m, then the time taken by the object to complete one revolution is:

T^{2} = \frac{4\pi^{2}\cdot R}{a}

T = 2\pi\cdot \sqrt{\frac{R}{a} }

T = 2\pi\cdot \sqrt{\frac{0.93\,m}{26.36\,\frac{m}{s^{2}} } }

T \approx 1.180\,s

The object takes approximately 1.180 seconds to complete one horizontal circle.  

7 0
3 years ago
Please help!!!! Will mark brainliest.
julia-pushkina [17]

Answer:

Approximately 8.4 \times 10^{2}\; \rm N, assuming that g = 9.8\; \rm m \cdot s^{-2}.

Explanation:

Let m and a denote the mass and acceleration of Spiderman, respectively.

There are two forces on Spiderman:

  • Downward gravitational attraction from the earth: W = m \cdot g.
  • Upward tension force from the strand of web F(\text{tension}).

The directions of these two forces are exactly opposite of one another. Besides, because Spiderman is accelerating upwards, the magnitude of F(\text{tension}) (which points upwards) should be greater than that of W (which points downwards towards the ground.)

Subtract the smaller force from the larger one to find the net force on Spiderman:

(\text{Net Force}) = F(\text{tension}) - W.

On the other hand, apply Newton's Second Law of motion to find the value of the net force on Spiderman:

(\text{Net Force}) = m \cdot a.

Combine these two equations to get:

m \cdot a = (\text{Net Force}) = F(\text{tension}) - W.

Therefore:

\begin{aligned}& F(\text{tension})\\ &= m \cdot a + W \\ &= m \cdot (a + g)\\ &= 76\; \rm kg \times \left(1.3\; \rm m \cdot s^{-2} + 9.8\; \rm m \cdot s^{-2}\right)\\ &\approx 8.4\times 10^{2}\; \rm N\end{aligned}.

By Newton's Third Law of motion, Spiderman would exert a force of the same size on the strand of web. Hence, the size of the force in the strand of the web should be approximately 8.4\times 10^{2}\; \rm N (downwards.)

4 0
3 years ago
What happens when an object is dropped? A. It decelerates at a rate of 9.8 m/s/s. B. It travels 9.8 meters before stopping. C. I
andreev551 [17]
I think its c I really don't take physics but I try to help.
5 0
3 years ago
Describe five things that you do to make yourself feel warmer or cooler.
stira [4]
Buy a fan or heater, get a blanket, take a shower, go outside, go by the fireplace
7 0
3 years ago
Drawing a ray diagram for an object far from convex lens requires how many rays?
Crank

Answer

4

Explanation:

four rays can also explain the ray diagram if the object is at infinity

5 0
2 years ago
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