Physics Phail

Easy physics question, but I fail:

Q: A sparrow’s maximum air speed is 10m/s. She wants to fly to her nest 10m due north, but there is a wind blowing from W to E at 10m/s. What direction should she fly?

A: It can’t be done. Velocity will be northeast.


Seriously. Physics 1. I hate physics.  I liek math.

Aw sit, nikka.

The question was: why can't it be done? Why can't the sparrow fly 45 degrees west of north?

poop

Because the wind is too fast. If the sparrow flies in any direction except west, its east-to-west speed is less than 10m/s, so the wind will always be pushing the sparrow to the east.

why the hell would the windspeed at 10m/s mean that the bird will be pushed 10m/s by the wind?

>>5
Because it's a piece of shit word problem that's supposed to give you practice mapping a real-world example into a simpler abstract world to reason in, but usually ends up vague and confusing and making people ask the same sort of question you just did.

>>5
What's stopping it from being pushed?

>>7

Just because the wind speed is 10m/s doens't mean everything that the wind touches will then travel at 10m/s

For example, you walk with a velovity of 10m/s north, with a wind of 10m/s a second blowing W to E. The wind won't do shit to you, but it would with a flying sparrow.

We don't know the aerodynamic properties of this sparrow, so the question's fail.

The wind won't do shit to you
Because of the force from the ground (friction).

Aerodynamics affect the energy transfer, but unless the bird provides a counter force, eventually it will match the wind velocity (or more realistically, drop to the ground). Of course the bird does provide a force, but as per the question, not enough to overcome it.

so you're saying the wind can accelerate the bird fast enough to prevent it from reaching a nest 10 m away?

>>10
Its maximum air speed is 10m/s. If it were flying directly into the wind at maximum speed, it's speed relative the ground would be 0. Any deviation of its direction will decrease the component of its velocity parallel to the wind, and will therefore cause the bird to start moving towards the east.

Since the question is phrased purely in terms of speeds, acceleration is irrelevant.

>>11
acceleration is not irrelevant.  the wind moving at 10m/s applies a particular force against the bird, which will amount to a certain acceleration, dependent on that force and the mass of the bird.  you are suggesting that this force instantly accelerates the bird to 10m/s.  is it not possible that, depending on the mass of the bird, it may be able to fly directly west, before reaching velocity relative to the ground east-west, and then turn slightly north, begin to have an easterly velocity relative to the ground, while also maintaining a slight velocity toward the north.  depending on how fast the bird can accelerate itself to 10m/s, how fast the wind could accelerate the bird to 10m/s, the bird might be able to get to the nest.

it may be able to fly directly west
Then it would have an air speed > 10m/s, which cannot happen according to the question.

You all fucking fail. It's a simple vector addition problem.

>>12
You, in particular, fail completely.

Given that the question doesn't ask for the quickest path, the simplest directions would be to fly facing due north at 10m/s for one second (for a net velocity of 10sqrt(2) NE), and then fly due east until it reaches the nest.  And yes, it does reach the nest... ;)

If you want a single heading, you'll have to know the latitude at which this is happening so you can work out the circumference of the path around the earth.  (It's due east, which isn't a great circle unless you're on the equator.)

Now if you assume the question is in a hypothetical flat Cartesian world (as the question probably intends but doesn't specify), then the answer is - as others have said - that it can't be done.

>>13
>>14

You both don't know how to read.

I think she could make it, acceleration is important here and I think the thrust from her would negate a lot of the force from the wind.

mass and air resistance would be factors so I think the ``answer'' is wrong in stating that it isn't possible.

The birds maximum air speed is equal to the current wind speed.  Therefore, it is impossible for the bird to make any significant gains in the westerly direction.  The best the bird could hope for is a surge to gain a small distance, and then stalemate the wind heading directly west.

This shitty picture is how things would turn out.  The bird would take off, and the wind would push her only slightly off course.  She'd land either on the east edge of her nest, or be over powered by the wind and barely miss, landing on the 'X'.  She wouldn't be pushed right at 10m/s, but it would probably be enough to make her miss.

Nest:
---------(######)-X-
}
}
}
}
}
}
}
----------- \^/ --
Bird


But remember, this is a beginning, high school level physics course.  These kids haven't even learned F=ma yet.  This is a simple problem to introduce vectors, so its assumed that the wind instantly accelerates the bird to 10m/s as soon as she takes flight.

African, or European?

How do know so much about swallows?

Well, you have to know these things when you're a king, you know.

yeah it would be impossible if max speed was 10mperS cuz it'd have to fly 10mperS west in order to stay in the same position, if it tried to fly north at all it would loose speed in the west direction and be blown towards the east.

btw 10mperS for a bird is fucking fast...

>>21
IN BEFORE COCONUTS

>>22
36 km/h is not that fast for a bird.