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3 years ago

Select the correct answer.

Physics

1 answer:

Naddika [18.5K]3 years ago

6 0

Answer:77J in 2 s.f.

Explanation:

Use formula,

E = ( O / I ) * 100%

Where,

E = efficiency

O = Output

I = Input

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A bat locates insects by emitting 25.3 kHz ultrasonic chirps and then listening for echoes from insects flying around it. Humans

mote1985 [20]

Answer:

Speed at which the bat have to fly is 90.895 m/s away from the human (listener) in positive direction.

Explanation:

Given:

Frequency of the bat that is source here, $f_S$ = 25.3 kHz = 25.3 * 10^3 Hz

Frequency of the listener (human), $f_L$ = 20 kHz = 20*10^3 Hz

We have to identify how fast the bat have to fly in order for a person to hear these chirps .

Let the velocity of bat that is source is "Vs" and "Vs" = "Vbat".

Doppler effects formulae :

When the source is receding (moving away) $f_L=(\frac{V+V_L}{V+V_S}) f_S$
When the source is approaching $f_L=(\frac{V+V_L}{V-V_S}) f_S$
Speed of sound in $V_S =433.895-343$ the air (medium), $V = 343\ ms^-^1$

Using the above formula and considering that the bat is moving away so that the human can listen the chirps also $V_L=0$ as listener is stationary.

⇒ $f_L=(\frac{V+V_L}{V+V_S}) f_S$ ⇒ $f_L=(\frac{V+0}{V+V_S}) f_S$

Re-arranging in terms of Vs.

⇒ $V+V_S =\frac{V\times f_S}{f_L}$

⇒ $V_S =\frac{V\times f_S}{f_L}-V$

⇒ $V_S =\frac{343\times 25.3\times 10^3}{20\times 10^3}-343$

⇒ $V_S=90.895$ m/s

The speed at which the bat have to fly is 90.895 m/s away from the human (listener) in positive direction.

7 0

3 years ago

What is the normal force acting on a 65 kg desk?

Aneli [31]

Normal force is an equal but opposite force to weight.

Weight = Normal force

weight=m×g

= 65×10

=650N

Explanation:

HOPE THAT THIS IS HELPFUL.

HAVE A GREAT DAY.

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If two carts collide, what type of collision will conserve both momentum and kinetic energy?

Naya [18.7K]

For the first one I believe it would be D. And for 39 it would be c

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A 1200 kg car traveling east at 4.5 m/s crashes into the side of a 2100 kg truck that is not moving. During the collision, the v

zhenek [66]

Answer:

yyyggggggggggggggthhgggggyyyyy

Explanation:

yyygggggggggggg

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Mila [183]

the question is correct

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