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3 years ago

In which activity is no work done?

Physics

2 answers:

Doss [256]3 years ago

5 0

Answer: The correct option is B.

Explanation:

Work is done when the force is applied to move an object to certain distance.

In the case of lifting a book, the work is done as the force is applied to lift the book. There will be displacement.

In the case of holding a brick, no work is done as the force is applied in this case but there is no displacement.

In the case of climbing stairs, work is done in climbing the stairs as the force is acting here. There will be displacement when the man will climb.

In the case of pushing a shopping cart, the work is done as the force is applied to a shopping cart. There will be displacement in forward direction.

Therefore, the correct answer is B.

sleet_krkn [62]3 years ago

3 0

The answer is B because you are not using force or energy as if you were if you were to lift or push something.

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If a nearsighted person has a far point df that is 3.50m from the eye, what is the focal length f1 of the contact lenses that th

olga55 [171]

Answer:

f1= -350cm or -3.5m

f2= 22.1cm or 0.221m

Explanation:

A person is nearsighted when the person's far point is less than infinity. A diverging lens is normally used to correct this eye defect. A diverging lens has a negative focal length as seen in the solution attached.

Farsightedness is when a person's near point is farther than 25cm. This eye defect is corrected using a converging lens. The focal length of a converging lens is positive. This is evident in the solution attached. The near point is also referred to as the least distance of distinct vision.

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3 years ago

If 270 watts of power is used in 42 seconds, how much work was done

navik [9.2K]

Answer: W = 11340J

Explanation:

Hey there! I will give the following steps, if you have any questions feel free to ask me in the comments below.

So this is the Formula: Power = Work / Time.

Step 1: Find the Formula

P = W / T

Step 2: Make W the subject of the equation.

W = PT

Step 3: Given.

P = 270 Watts, T = 42 seconds

Step 4: Substitute these values into equation 2 .

W = 270(42)

Step 5: Simplify.

W = 11340J

The amount of work done was 11340.

~I hope I helped you! :)~

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3 years ago

The decibel level of an orchestra is 90 db, and the violin section achieves a level of 80 dB. How does the sound intensity from

skad [1K]

Answer:

The difference in the decibel corresponses to a constant difference in the loudness perceived.

The refore the sound intensity from the orchestra is like 100 times that of the violin.

Explanation:

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3 years ago

You walk 20 m north then 30 m west for a total timer four minutes what is the magnitude of your average velocity in (m/s)

Shalnov [3]

Answer:

The average velocity is 0.15 m/s

Explanation:

Use the definition of average velocity as the distance traveled divided the time it took.

Since the movement was on the plane from the origin (0, 0) to the point (-30, 20) corresponding to 30 m west and 20 m north, we calculate the distance using the distance between two points on the plane:

$distance=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2} = \sqrt{(-30)^2+20^2} =\sqrt{1300} \approx 36.06\,\,m$

Then the magnitude of the average velocity can be estimated via the quotient between distance divided time, but since the units required are meters per second, we first convert the four minute time into seconds: 4 * 60 = 240 seconds.

Then the average velocity becomes:

$v_{ave}=\frac{distance}{time} =\frac{36.06}{240} =0.15\,\,m/s$

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3 years ago

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