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2 years ago

5

A woman hikes 2.5 kilometers in 30 minutes, and then 3 kilometers in 20 minutes, and finally 2 kilometers in 10 minutes. What wa

s her average speed?

1 answer:

nalin [4]2 years ago

3 0

Answer:

7.5 kph

Explanation:

2.5+3+2=7.5

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A train whistle is heard at 300 Hz as the train approaches town. The train cuts its speed in half as it nears the station, and t

givi [52]

To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is the change in the perceived frequency of any wave movement when the emitter, or focus of waves, and the receiver, or observer, move relative to each other. Mathematically it can be described as,

$f = f_0 (\frac{v_0}{v_0-v})$

Here,

$f_0$ = Frequency of Source

$v_s$ = Speed of sound

f = Frequency heard before slowing down

f' = Frequency heard after slowing down

v = Speed of the train before slowing down

So if the speed of the train after slowing down will be v/2, we can do a system equation of 2x2 at the two moments, then,

The first equation is,

$f = f_0 (\frac{v_0}{v_0-v})$

$300 = f_0 (\frac{343}{343-v})$

$(300*343) - 300v = 343f_0$

Now the second expression will be,

$f' = f_0 (\frac{v_0}{v_0-v/2})$

$290 = (343)(\frac{v_0}{343-v/2})$

$290*343-145v = 343f_0$

Dividing the two expression we have,

$\frac{(300*343) - 300v}{290*343-145v} = 1$

Solving for v, we have,

$v = 22.12m/s$

Therefore the speed of the train before and after slowing down is 22.12m/s

6 0

2 years ago

PLEASE HELP ILL MARK BRAINLIEST

ikadub [295]

I think the answer is A?

7 0

2 years ago

The argument against your claim (what the other side would say if they disagreed with your claim.) is:

Vlad1618 [11]

Answer:

a counterclaim

Explanation:

authors purpose is what an author wrote somthing for

opinion is someones thoughts or "side" on a argument

an arguement is a battle of opinions if that makes sense

3 0

2 years ago

Which transformation of energy occurs when a fan is turned on and the blades start to rotate?

Ksju [112]

Answer:

kinetic energy

Explanation:

A wind turbine transforms the mechanical energy of wind into electrical energy. A turbine takes the kinetic energy of a moving fluid, air in this case, and converts it to a rotary motion. As wind moves past the blades of a wind turbine, it moves or rotates the blades. These blades turn a generator

5 0

2 years ago

Which vector below goes from (0,0) to (1,-3)?

vitfil [10]

I think D. It starts at (0.0) and goes to the correct points so it makes sense

8 0

3 years ago

Read 2 more answers