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My name is Ann [436]
2 years ago
13

Please help me with this question guys.

Physics
1 answer:
katen-ka-za [31]2 years ago
7 0

Answer:

<em>The average speed is 22.2 km/h</em>

Explanation:

<u>Average Speed</u>

Given an object travels a total distance d and took a total time t, then the average speed is:

\displaystyle \bar v=\frac{d}{t}

The mailman first drives d1=7 km at v1=15 km/h. The time taken to drive is:

\displaystyle t1=\frac{d1}{v1}=\frac{7}{15}=0.467\ h

Then he drives d2=7 km at v2=43 km/h taking a time of:

\displaystyle t2=\frac{d2}{v2}=\frac{7}{43}=0.163\ h

The total time is

t=0.467 h + 0.163 h = 0.63 h

The total distance is

d = 7 km + 7 km = 14 km

The average speed is:

\displaystyle \bar v=\frac{14}{0.63}=22.2\ km/h

The average speed is 22.2 km/h

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siniylev [52]
Sdhdmzir d sjdurkshrjeidnrjddneuxneixfnsidnrjxcbfnxudnx
4 0
3 years ago
What is the period of a soundwave whose wavelength is 20.0 m? Use values from the book and show ALL of your work.
Liono4ka [1.6K]
<h3><u>Answer;</u></h3>

Period = 1/17 seconds

<h3><u>Explanation;</u></h3>
  • Wavelength is related to period by the expression:

<em>speed = wavelength / period </em>

  • If we are given the speed, then we can easily calculate the period at the wavelength of 20 m.

<em>Given the speed of sound wave as 340 m/s </em>

<em>Period = Wavelength/ speed</em>

<em>            = 20 m/340 m/s</em>

<em>            </em><u><em>= 1/17 seconds</em></u>

7 0
2 years ago
Honeybees accumulate charge as they fly, and they transfer charge to the flowers they visit. Honeybees are able to sense electri
Vilka [71]

Answer:

ΔE> E_minimo

We see that the field difference between these two flowers is greater than the minimum field, so the bee knows if it has been recently visited, so the answer is if it can detect the difference

Explanation:

For this exercise let's use the electric field expression

         E = k q / r²

where k is the Coulomb constant that is equal to 9 109 N m² /C², q the charge and r the distance to the point of interest positive test charge, in this case the distance to the bee

let's calculate the field for each charge

 

Q = 24 pC = 24 10⁻¹² C

         E₁ = 9 10⁹ 24 10⁻¹² / 0.20²

         E₁ = 5.4 N / C

Q = 32 pC = 32 10⁻¹² C

         E₂ = 9 10⁹ 32 10⁻¹² / 0.2²

         E₂ = 7.2 N / C

let's find the difference between these two fields

         ΔE = E₂ -E₁

         ΔE = 7.2 - 5.4

         ΔE = 1.8 N / C

the minimum detection field is

         E_minimum = 0.77 N / C

        ΔE> E_minimo

We see that the field difference between these two flowers is greater than the minimum field, so the bee knows if it has been recently visited, so the answer is if it can detect the difference

8 0
2 years ago
PLEASE ANSWER FAST In which of the following situations is the greatest amount of work accomplished? 1. A boy lifts a 2-newton b
GuDViN [60]

Explanation:

Work done is given by the product of force and displacement.

Case 1,

1. A boy lifts a 2-newton box 0.8 meters.

W = 2 N × 0.8 m = 1.6 J

2. A boy lifts a 5-newton box 0.8 meters.

W = 5 N × 0.8 m = 4 J

3. A boy lifts a 8-newton box 0.2 meters.

W = 8 N × 0.2 m = 1.6 J

4. A boy lifts a 10-newton box 0.2 meters.

W = 10 N × 0.2 m = 2 J

Out of the four options, in option (2) ''A boy lifts a 5-newton box 0.8 meters'', the work done is 4 J. Hence, the greatest work done is 4 J.

3 0
3 years ago
What is the magnitude of an electric field that balances the weight of a plastic sphere of mass 2.1 g that has been charged to -
Liula [17]

Answer:

Electric field, E=6.86\times 10^6\ N/C

Explanation:

It is given that,

Mass of sphere, m = 2.1 g = 0.0021 kg

Charge, q=-3\ nC=-3\times 10^{-9}\ C

We need to find the magnitude of electric field that balances the weight of a plastic spheres. So,

ma=qE

a = g

E=\dfrac{mg}{q}

E=\dfrac{0.0021\ kg\times 9.8\ m/s^2}{-3\times 10^{-9}\ C}

E=6860000\ N/C

or

E=6.86\times 10^6\ N/C

Hence, the magnitude of electric field that balances its weight is 6.86\times 10^6\ N/C. Hence, this is the required solution.

4 0
3 years ago
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