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Salsk061 [2.6K]

2 years ago

9

a bus travelling on a straight road at 25m/s accelerates uniformly at 5m/s squared for 2 seconds. find its speed in kilometres p

er hour

1 answer:

notka56 [123]2 years ago

5 0

Answer:

126 kmh⁻¹

Explanation:

We can simply solve this by applying motion equations

where

v - final velocity

u - initial velocity

a-acceleration

t - time

v = u + at

<em>= 25 + 5×2 = 35 ms⁻¹</em>

<em> = (35/1000)×3600 = 126 kmh⁻¹</em>

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Read 2 more answers

You are trying to overhear a juicy conversation, but from your distance of 20.0 m , it sounds like only an average whisper of 30

12345 [234]

Answer:

r₂ = 0.2 m

Explanation:

given,

distance = 20 m

sound of average whisper = 30 dB

distance moved closer = ?

new frequency = 80 dB

using formula

$\beta = 10 log(\dfrac{I_1}{I_0})$

I₀ = 10⁻¹² W/m²

now,

$30 = 10 log(\dfrac{I_1}{10^{-12}})$

$\dfrac{I_1}{10^{-12}}= 10^3$

$I_1= 10^{-8}\ W/m^2$

to hear the whisper sound = 80 dB

$80 = 10 log(\dfrac{I_2}{10^{-12}})$

$\dfrac{I_2}{10^{-12}}= 10^8$

$I_2= 10^{-4}\ W/m^2$

we know intensity of sound is inversely proportional to square of distances

$\dfrac{I_1}{I_2}=\dfrac{r_2^2}{r_1^2}$

$\dfrac{10^{-8}}{10^{-4}}=\dfrac{r_2^2}{20^2}$

$10^{-4}=\dfrac{r_2^2}{20^2}$

r₂ = 0.2 m

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3 years ago