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3 years ago

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Help please:A boy weighing 30 kg rides a scooter. The total kinetic energy of the boy and the scooter is 437.6 J. Determine the

speed at which the boy moves if the mass of the scooter is 5kg?

2 answers:

Ksenya-84 [330]3 years ago

5 0

Answer:

the total mass is 35 kg

k.E = 1/2 mv2

43.76 =1/2 v2

v2=2×43.76

Explanation:

v=radicls 87.52 which is equal to 9.5 m/s

larisa86 [58]3 years ago

3 0

Answer:

5 m/s

Explanation:

Mass of the boy + scooter system = 35 kg

Kinetic Energy = 437.6 J

437.6 = $\frac{1}{2} 35 {v}^2$

25.0057143 = $v^{2}$

v = 5 m/s

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Answer:

The amplitude is $A = 90.2 \ m$

Explanation:

From the question we are told that

The frequency of when sound is approaching observer is $f = 392 Hz$

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The time between the pitch are $t = 10 \ s$

Here you are the observer and your friends are the source of the sound

The period is mathematically evaluated as

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as it is the time to complete one oscillation which from on highest pitch to the next highest pitch

Now T can also be mathematically represented as

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Where $w$ is the angular velocity

=> $\frac{2 \pi}{w} = 2 * 10$

=> $w = 0.314 \ rad/sec$

Now using Doppler Effect,

The source of the sound is approaching the observer

The

$f = f_o (\frac{v}{v- wA} )$

$392 = f_o (\frac{v}{v- wA} )$

Where A is the amplitude

So when the source is moving away from the observer

$f_a = f_o (\frac{v}{v+ wA} )$

$330 = f_o (\frac{v}{v+ wA} )$

Here $f_o$ is the fundamental frequency

Dividing the both equation we have

$\frac{392}{330} = \frac{f_o(\frac{v}{v-wA} )}{f_o(\frac{v}{v+wA}}$

$1.1878 = \frac{v+wA}{v-wA}$

$1.1878 v - 1.1878 wA = v+wA$

$1.1878 v = 2.1878 wA$

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