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Nina [5.8K]
2 years ago
9

A boy stands at a certain distance from a large building and blows a whistle. After 2.3s he hears the echo of the sound. He move

s 50m towards the building and blows his whistle again; this time the echo reaches him after 2.0s. Calculate thei. Boys original distance from the building ii. Speed of sound in air
Physics
1 answer:
ddd [48]2 years ago
6 0

Answer:

I) 57.5 m

Il) 50 m/s

Explanation:

Given that a boy stands at a certain distance from a large building and blows a whistle.

After 2.3s he hears the echo of the sound. The speed V of the sound will be:

V = 2X / T

Where X is the distance covered

V = 2X / 2.3

V = 0.87X ...... (1)

He moves 50m towards the building and blows his whistle again; this time the echo reaches him after 2.0s.

V = (2×50) / 2

V = 50 m/s

Substitutes the V into equation 1

50 = 0.87X

X = 50 / 0.87

57.5 m

Therefore, the Boys original distance from the building is 57.5m and the

Speed of sound in air is 50m/s

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Answer:

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Explanation:

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F=\frac{GMm}{r^2}

where G=6.67\times10^{-11}Nm^2/kg^2 is the gravitational constant.

This force is the centripetal force the satellite experiments, so we can write:

F=ma_{cp}=mr\omega^2=mr(\frac{2\pi}{T})^2=\frac{4\pi^2mr}{T^2}

Putting all together:

\frac{GMm}{r^2}=\frac{4\pi^2mr}{T^2}

which means:

r=\sqrt[3]{\frac{GM}{4\pi^2}T^2}

Which for our values is:

r=\sqrt[3]{\frac{(6.67\times10^{-11}Nm^2/kg^2)(6.39\times10^{23} kg)}{4\pi^2}(1.026\times24\times60\times60s)^2}=20395282m=20395.3km

Since this distance is measured from the center of Mars, to have the height above the Martian surface we need to substract the radius of Mars R=3389.5 km , which leaves us with:

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6 0
2 years ago
Two objects are placed in thermal contact and are allowed to come to equilibrium in isolation. the heat capacity of object a is
Harman [31]
Given:
Ca = 3Cb                      (1)
where
Ca =  heat capacity of object A
Cb =  heat capacity f object B

Also,
Ta = 2Tb                     (2)
where
Ta = initial temperature of object A
Tb = initial temperature of object B.

Let
Tf =  final equilibrium temperature of both objects,
Ma = mass of object A,
Mb = mass of object B.

Assuming that all heat exchange occurs exclusively between the two objects, then energy balance requires that
Ma*Ca*(Ta - Tf) = Mb*Cb*(Tf - Tb)           (3)

Substitute (1) and (2) into (3).
Ma*(3Cb)*(2Tb - Tf) = Mb*Cb*(Tf - Tb)
3(Ma/Mb)*(2Tb - Tf) = Tf - Tb

Define k = Ma/Mb, the ratio f the masses.
Then
3k(2Tb - Tf) = Tf - Tb
Tf(1+3k) = Tb(1+6k)
Tf = [(1+6k)/(1+3k)]*Tb

Answer:
T_{f} =( \frac{1+6k}{1+3k} )T_{b}= \frac{1}{2}( \frac{1+6k}{1+3k})T_{a}
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7 0
2 years ago
An electric drill transfers 200 J of energy into a useful kinetic energy store. It also transfers 44 J of energy by sound and 48
kramer

Answer:

Er = 108 [J]

Explanation:

To solve this problem we must understand that the total energy is 200 [J]. Of this energy 44 [J] are lost in sound and 48 [J] are lost in heat. In such a way that these energy values must be subtracted from the total of the kinetic energy.

200 - 44 - 48 = Er

Where:

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kati45 [8]
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san4es73 [151]

Answer : The mass of ice melted can be, 3.98 grams.

Explanation :

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n = moles = ?

Now put all the given values in the above expression, we get:

27.2kJ=\frac{6.01kJ/mol}{n}

n=0.221mol

Now we have to calculate the mass of ice.

\text{Mass of ice}=\text{Moles of ice}\times \text{Molar mass of ice}

Molar mass of ice = 18.02 g/mol

\text{Mass of ice}=0.221mol\times 18.02g/mol=3.98g

Thus, the mass of ice melted can be, 3.98 grams.

3 0
2 years ago
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