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adoni [48]
3 years ago
6

You drive to the city at an average speed of 40 km/h and return at an average speed of 60 km/h. Find your average speed for the

entire trip? Explain why the answer is not 50 km/h.
Physics
1 answer:
Eva8 [605]3 years ago
7 0
Well, let's see:

If you live 'D' kilometers from the city, and you go and return by the same route, then

-- The time it takes you to reach the city, at 40 km/h, is  D/40  hours.

-- The time it takes you to return, at 60 km/h, is    D/60.

-- The total distance you cover is  2D, and the total driving time is

                        (D/40) + (D/60)

                   =  (3D/120)  +  (2D/120)

                   =        5D/120  =  D/24

-- Your average speed for the entire trip is

                         (distance covered)  /  (time to cover the distance)

                   =            ( 2D )   /   ( D/24 )

                   =              48 km/hr.  

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Lunna [17]

Answer:

   q = 224 mm,   h ’= - 98 mm, real imagen

Explanation:

For this exercise let's use the constructor equation

        \frac{1}{f} = \frac{1}{p} + \frac{1}{q}

       

where f is the focal length, p and q are the distance to the object and the image respectively.

In a mirror the focal length is

        f = R / 2

indicate us radius of curvature is equal to the diameter of the eye

       R = 3,50  10² mm

       f = 3.50 10² /2 = 1.75 10² mm

they also say that the distance to the object is p = 0.800 10³ mm

        1 / q = 1 / f - 1 / p

        1 / q = 1 / 175 - 1 /800

        1 / q = 0.004464

         q = 224 mm

to calculate the size let's use the magnification ratio

          m = \frac{h'}{h} = - \frac{q}{p}

          h '= - \frac{q}{p} \ h

          h ’= - 224 350 / 800

          h ’= - 98 mm

in concave mirrors the image is real.

3 0
3 years ago
Why does a light go out when you turn off the wall switch?
Nadusha1986 [10]
A light goes out when you turn off the wall switch because <u />B. the switch causes a break in the circuit.
Since there is a break in the circuit, electricity cannot come through to the bulb, which is why there is no light anymore.
8 0
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A bullet with a mass of 0.02 kg is fired horizontally into a block of wood hanging on a string. The bullet sricks in the wood an
djyliett [7]

Answer:

u= 20.09 m/s

Explanation:

Given that

m = 0.02 kg

M= 2 kg

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Lets take initial speed of bullet = u m/s

The final speed of the system will be zero.

From energy conservation

1/2 m u²+ 0 = 0+ (m+M) g h

m u²=2 (m+M) g h

By putting the values

0.02 x u² = 2 (0.02+2) x 10 x 0.2       ( take g=10 m/s²)

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7 0
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andriy [413]

Answer:

196

Explanation:

subtract 24 from 220 to get your answer.

6 0
2 years ago
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Finish the sentence below with the word that makes the sentence true.
Keith_Richards [23]

Answer:

Animals must eat other plants or animals to obtain the <u>energy</u> stored in the food

Explanation:

One classification of living organisms, according to the way they obtain energy, is that of autotrophs and heterotrophs. The first group is represented by plants, which process their own nutrients from inorganic matter.

<u>Animals -heterotrophes- are unable to process their own nutrients</u>, so they must obtain them from other organisms, either plants or animals. External food sources provide them with nutrients, which contain the energy substrate needed to perform their vital functions.

Learn more:

Autotrophs and heterotrophs brainly.com/question/7695115

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