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3 years ago

As the ambulance got closer, Marge noticed that the pitch of the siren got higher. This happened because

Physics

2 answers:

disa [49]3 years ago

7 0

Answer:

The correct choice is

A) the sound waves were pushed closer together.

Explanation:

As the ambulance gets closer, the distance between the ambulance and marge decreases and so does the wavelength of the siren observed by marge. As the wavelength decrease and speed remains the same for the siren, the frequency of the siren increases because wavelength, frequency and speed are related as

Frequency = Speed/wavelength

Clearly, the frequency is inversely related to wavelength.

AfilCa [17]3 years ago

6 0

A) the sound waves were pushed closer together

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A DJ starts up her phonograph player. The turntable accelerates uniformly from rest, and takes t1 = 11.9 seconds to get up to it

Degger [83]

Answer:

a) $\omega_1=8.168\,rad.s^{-1}$

b) $n_1=7.735 \,rev$

c) $\alpha_1 =0.6864\,rad.s^{-2}$

d) $\alpha_2=4.1454\,rad.s^{-2}$

e) $t_2=1.061\,s$

Explanation:

Given that:

initial speed of turntable, $N_0=0\,rpm\Rightarrow \omega_0=0\,rad.s^{-1}$

full speed of rotation, $N_1=78 \,rpm\Rightarrow \omega_1=\frac{78\times 2\pi}{60}=8.168\,rad.s^{-1}$

time taken to reach full speed from rest, $t_1=11.9\,s$

final speed after the change, $N_2=120\,rpm\Rightarrow \omega_2=\frac{120\times 2\pi}{60}=12.5664\,rad.s^{-1}$

no. of revolutions made to reach the new final speed, $n_2=11\,rev$

(a)

∵ 1 rev = 2π radians

∴ angular speed ω:

$\omega=\frac{2\pi.N}{60}\, rad.s^{-1}$

where N = angular speed in rpm.

putting the respective values from case 1 we've

$\omega_1=\frac{2\pi\times 78}{60}\, rad.s^{-1}$

$\omega_1=8.168\,rad.s^{-1}$

(c)

using the equation of motion:

$\omega_1=\omega_0+\alpha . t_1$

here α is the angular acceleration

$78=0+\alpha_1\times 11.9$

$\alpha_1 = \frac{8.168 }{11.9}$

$\alpha_1 =0.6864\,rad.s^{-2}$

(b)

using the equation of motion:

$\omega_1\,^2=\omega_0\,^2+2.\alpha_1 .n_1$

$8.168^2=0^2+2\times 0.6864\times n_1$

$n_1=48.6003\,rad$

$n_1=\frac{48.6003}{2\pi}$

$n_1=7.735\, rev$

(d)

using equation of motion:

$\omega_2\,^2=\omega_1\,^2+2.\alpha_2 .n_2$

$12.5664^2=8.168^2+2\alpha_2\times 11$

$\alpha_2=4.1454\,rad.s^{-2}$

(e)

using the equation of motion:

$\omega_2=\omega_1+\alpha_2 . t_2$

$12.5664=8.168+4.1454\times t_2$

$t_2=1.061\,s$

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3 years ago

Help with question 16 and 17

storchak [24]

Your answer is correct.

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The fractional change in resistance is equal to the given temperature coefficient multiplied by the change in temperature.

R = R₀×(1 + α×ΔT)

R = (10.0 Ω)×(1 + 0.004×(65 -20)) = 11.8 Ω

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3 years ago

Why is it important that two different metals are used in building an electrochemic<br> cell?

Mnenie [13.5K]

Answer:

Explanation:

They need a galvanic difference. Or saying that less technically, they need to have different electron attraction, so that one can collect electrons (oxidation/reduction) and flow current from the other. :)

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2 years ago

A ball rolls down a ramp. A small amount of friction heats up the ball. What energy transformations are taking place?

Natasha2012 [34]

Answer:kinetic energy converted to heat energy

Explanation:

As the ball rolls down kinetic energy is converted to heat energy

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3 years ago

Read 2 more answers

Can someone help with this???

Rus_ich [418]