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Gre4nikov [31]
3 years ago
7

One brand of dog whistles claims a frequency of 25 kHz for its product. What is the wavelength of this sound? (the speed of soun

d in air is 343 m/s)
0.01372 m
0.02181 m
0.01748 m
0.011654 m
Physics
1 answer:
Alex787 [66]3 years ago
4 0

Answer:

Option A

0.01372 m

Explanation:

The speed of sound is a product of the wavelength and frequency hence

Speed=Wavelength * Frequency

Making wavelength the subject then

Wavelength=\frac {speed}{frequency}

Substituting 343 m/s for speed and 25 kHz= 25000 Hz for frequency we obtain

Wavelength=\frac {343}{25000}=0.01372 m

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Answer:

c. length of the wall or column and the rate of placement of the concrete

Explanation:

when designing for wall and column form-works, it is of utmost important to know the length of the wall and the type of concrete placement to be used.

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How much heat is required to heat 2 kg of water from 25°C to 40°C?
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Answer:

126000 J

Explanation:

Applying,

Q = cm(t₂-t₁).................. Equation 1

Where Q = Amount of heat, c = specifc heat capacity of water, m = mass of water, t₁ = Initial temperature, t₂ = Final temperature.

From the question,

Given: m = 2 kg, t₁ = 25°C, t₂ = 40°C

Constant: c = 4200 J/kg.°C

Substitute these value into equation 1

Q = 2×4200(40-25)

Q = 2×4200×15

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A car travels a distance of 100 km. For the first 30 minutes it is driven at a constant speed of 80 km/hr. The motor begins to v
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Explanation:

First, we need to determine the distance traveled by the car in the first 30 minutes, d_{\frac{1}{2}}.

Notice that the unit measurement for speed, in this case, is km/hr. Thus, a unit conversion of from minutes into hours is required before proceeding with the calculation, as shown below

                                          d_{\frac{1}{2}\text{h}} \ = \ \text{speed} \ \times \ \text{time taken} \\ \\ \\ d_{\frac{1}{2}\text{h}} \ = \ 80 \ \text{km h}^{-1} \ \times \ \left(\displaystyle\frac{30}{60} \ \text{h}\right) \\ \\ \\ d_{\frac{1}{2}\text{h}} \ = \ 80 \ \text{km h}^{-1} \ \times \ 0.5 \ \text{h} \\ \\ \\ d_{\frac{1}{2}\text{h}} \ = \ 40 \ \text{km}

Now, it is known that the car traveled 40 km for the first 30 minutes. Hence, the remaining distance, d_{\text{remain}} , in which the driver reduces the speed to 40km/hr is

                                             d_{\text{remain}} \ = \ 100 \ \text{km} \ - \ 40 \ \text{km} \\ \\ \\ d_{\text{remain}} \ = \ 60 \ \text{km}.

Subsequently, we would also like to know the time taken for the car to reach its destination, denoted by  t_{\text{remian}}.

                                              t_{\text{remain}} \ = \ \displaystyle\frac{\text{distance}}{\text{speed}} \\ \\ \\ t_{\text{remain}} \ = \ \displaystyle\frac{60 \ \text{km}}{40 \ \text{km hr}^{-1}} \\ \\ \\ t_{\text{remain}} \ = \ 1.5 \ \text{hours}.

Finally, with all the required values at hand, the average speed of the car for the entire trip is calculated as the ratio of the change in distance over the change in time.

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Therefore, the average speed of the car is 50 km/hr.

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C. The number of F atoms in the reactants equals the number of F atoms in the products.

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