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Travka [436]
3 years ago
12

A person watches an ambulance drive by them while emitting a steady sound from its siren. When the ambulance passes the person (

switching from moving towards him to moving away from him), the perceived frequency of the sound he receives decreases by 11.2 percent. How fast is the ambulance driving
Physics
1 answer:
Dmitrij [34]3 years ago
6 0

Answer:

21.7 m/s

Explanation:

Let the velocity of ambulance is v and f is the real frequency of siren of ambulance.

the velocity of sound is 343 m/s

use the formula of Doppler's effect

f' = \frac{343}{343-v}f    .... (1)

where, f' is the frequency of at the first time.

Now the source is moving away from the person, the frequency is given by

f'' = \frac{343}{343+v}f    .... (2)

According to the question,

f'' = f' - 11.0 % of f'

f'' = 0.881 f'

By equation (1) and (2)

\frac{343}{343+v}f= \frac{343}{343-v}\times 0.881f

40.817 = 1.881 v

v = 21.7 m/s

Thus, the speed of ambulance is 21.7 m/s.

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When a ball is launched from the ground at a 45° angle to the horizontal, it falls back to the ground 50 m from the launch point
Inessa [10]

Answer:

Explanation:

Given

angle through which ball is launched=45^{\circ}

Range of ball=50 m

Range of projectile is =\frac{u^2sin2\theta }{g}

50=\frac{u^2sin90}{9.8}

u=22.136 m/s

If ball is thrown straight upward

v^2-u^2=2as

0-(22.136)^2=2(-9.8)s

s=\frac{22.136^2}{2\times 9.8}

s=25 m

(b)For Projectile time of flight is

t=\frac{2usin\theta }{g}

t=\frac{2\times 22.136\times sin45}{9.8}

t=3.19 s

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3 years ago
Force is measured in units called
balu736 [363]

Answer:

Newtons

Explanation:

8 0
3 years ago
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Inside most ball-point pens is a small spring that compresses as the pen is pressed against the paper. If a force of 0.1 N compr
AnnZ [28]

Answer:

20 N/m

Explanation:

From the question,

The ball-point pen obays hook's law.

From hook's law,

F = ke............................ Equation 1

Where F = Force, k = spring constant, e = compression.

Make k the subject of the equation

k = F/e........................ Equation 2

Given: F = 0.1 N, e = 0.005 m.

Substitute these values into equation 2

k = 0.1/0.005

k = 20 N/m.

Hence the spring constant of the tiny spring is 20 N/m

8 0
3 years ago
Calculate the number of images formed by two plane mirrors inclined at angel of 18 to each other
allochka39001 [22]

Answer:

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Explanation:

Formula for number of images formed by two plane mirrors incident at an angle θ is n = 360∘θ. If n is even, the number of images is n-1, if n is an odd number of images.

4 0
3 years ago
A wire of length 5mm and Diameter 2m extends by 0.25 when a force of 50N was use. calculate the
bazaltina [42]

Answer and Explanation:

Data provided in the question

Force = 50N

Length = 5mm

diameter = 2.0m = 2\times 10^{-3}

Extended by = 0.25mm = 0.25\times 10^{-3}

Based on the above information, the calculation is as follows

a. The Stress of the wire is

= \frac{force\ applied}{area\ of \ circle}

here area of circle = perpendicular to the are i.e cross-sectional  i.e

= \frac{\pi d^{2}}{4}

= \frac{\pi(2\times 10^{-3})^2}{4}

Now place these above values to the above formula

= \frac{4\times 50}{\pi\times 4 \times 10^{-6}} \\\\ = \frac{50}{\pi}

= 15.92 MPa

As 1Pa = 1 by N m^2

So,

MPa = 10^6 N m^2

b. Now the strain of the wire is

= \frac{Change\ in\ length}{initial\ length} \\\\ = \frac{0.25\times 10^{-3}}{5}

= 5 \times 10^{-5}

3 0
3 years ago
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