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nata0808 [166]
3 years ago
15

riving you along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive the

frequency as 1370 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1330 Hz. What is the speed of the police car
Physics
1 answer:
Vaselesa [24]3 years ago
7 0

Answer:

The speed of the police car is 33.98 m/s

Explanation:

Given;

first speed, v₁ = 35 m/s

first frequency, f₁ = 1370 Hz

second frequency, f₂ = 1330 Hz

second speed, v₂ = ?

Speed of sound is directly proportional to its frequency;

v = fλ

assuming the λ is constant, then,

\lambda = \frac{V}{F}\\\\\frac{V_1}{F_1} = \frac{V_2}{F_2}\\\\V_2 = \frac{V_1F_2}{F_1}\\\\V_2 =   \frac{35*1330}{1370}\\\\V_2 = 33.98 \ m/s

Therefore, the speed of the police car is 33.98 m/s

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A shuttle bus slows down with an average acceleration of -2.4 m/s2. How long does it
olganol [36]

Answer:

\boxed {\boxed {\sf 3.75 \ seconds }}

Explanation:

Average acceleration is found by dividing the change in acceleration by the time.

a=\frac{ v_f-v_i}{t}

The shuttle bus has an acceleration of -2.4 meters per square second. It slows from 9.0 meters per second to rest, or 0 meters per second. Therefore:

a= -2.4 \ m/s^2 \\v_f= 0 \ m/s \\v_i= 9 \ m/s

Substitute the values into the formula.

-2.4 \ m/s^2=\frac{0 \ m/s - 9 \ m/s}{t }

Solve the numerator.

-2.4 \ m/s^2 = \frac{-9 \ m/s}{t}

We want to solve for t, the time. We have to isolate the variable. Let's cross multiply.

\frac{-2.4 \ m/s^2}{1} = \frac{-9 \ m/s}{t}

-9 \ m/s *1= -2.4 \ m/s^2 *t

-9 \ m/s=-2.4 m/s^2*t

t is being multiplied by -2.4. The inverse of multiplication is division, so divide both sides by -2.4

\frac{-9 \ m/s }{-2.4 \ m/s^2} =\frac{ -2.4 \ m/s^2*t}{-2.4 \ m/s^2}

\frac{-9 \ m/s }{-2.4 \ m/s^2} =t

3.75 \ s=t

It takes <u>3.75 seconds.</u>

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Explanation:

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8 0
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What is static electricity
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Example:  

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2) Comb your hair with a plastic comb then use it to pick up small pieces of paper. The comb picks up electrons from your hair and becomes negatively charged. It uses this charge to attract the pieces of paper.  

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3 0
3 years ago
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A merry-go-round a.k.a "the spinny thing" is rotating at 15 RPM, and has a radius of 1.75 m
arlik [135]

Answer:

A.) 4 revolution

B.) 0.2 revolution

C.) 4 seconds

D.) 2.75 m/s

Explanation:

Given that a merry-go-round a.k.a "the spinny thing" is rotating at 15 RPM, and has a radius of 1.75 m

Solution

1 revolution = 2πr

Where r = 1.75m

A. How many revolutions will it make in 3 minutes?

(2π × 1.75) / 3

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Number of revolution = 15 / 3.665

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B. How many revolutions will it make in 10.0 seconds?

First convert 10 seconds to minutes

10/60 = 0.167 minute

(2π × 1.75) / 0.167

10.9955 / 0.167

65.973

Number of revolution = 15 / 65.973

Number of revolution = 0.2 revolution

C. How long does it take for a person to make 1 complete revolution?

15 = 1 / t

Make t the subject of formula

t = 1/15

t = 0.0667 minute

t = 4 seconds

D. What is the velocity in m/s of person standing on its edge?

Velocity in m/ s will be:

Velocity = (15 × 2pi × r) / 60

Velocity = 164.9334 / 60

Velocity = 2.75 m/s

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4 0
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