Can a fly on an airplane fly faster than the airplane?

[dorkymichelle]

My dad asked me this yesterday,
if a fly(insect) flies from one end to the airplane to another, would it be flying faster than the airplane?
The obvious answer is no, it's physically impossible, but how do I articulate the reasoning, I know it has something to do with the reference frame of where the fly is flying...
but if you are on the ground and the airplane is clear and you see the fly flying, would it seem like the fly is flying faster than the plane?

 

[Lsos]

I guess it depends how you interpret the question.

To an observer on the ground the fly is indeed moving faster than the plane. When you walk to the bathroom on the plane you are also moving faster than the plane, although you are both ON the plane, so it won't be such a shock to the ground observer to find out your speeds.

To an observer on the plane, the plane is standing still, and the fly is moving. So again, the fly is moving faster. Again, it's not a shock because the observer on the plane understands that the fly is ON the plane, and he will give all the credit for the speed to the airplane, not the fly. The fly is not doing anything extraordinary. The airplane is. Indeed, the observer understands this so much that he will most likely switch reference frames when comparing their speeds: he will look out the window when checking how fast the airplane is moving, and he will look inside the cabin to see how fast the fly is "moving". He will then, for his own sanity, calculate that the plane is moving at ~500mph, where as the fly is "moving" at 1mph...although technically the fly is indeed moving at 501mph.

However, what does the word "flying" mean? Pilots are generally interested in their airspeeds...how fast they are moving with respect to the air that is directly around them. In this case the airplane is obviously "flying" faster than the fly...although the fly is still moving faster. That's probably what your concept of "flying" is, and hence why you think it's physically impossible for a fly to "fly" faster than a jet.

Sorry if I confused you, but as you said, it has to do with frames of reference. Strictly speaking, when comparing objects' speeds you should stick to one frame. For your own convenience, however, you may switch between frames but you should always be aware of doing so.

 

[pallidin]

This is, to me, a great example of "reference frames"

 

[BruceW]

from the perspective of someone on the ground, then yes, the fly is flying faster than the plane.

 

[DaveC426913]

The obvious answer is no, it's physically impossible,

Why? I am riding a train right now.

Are you telling me it is physically impossible for me to be moving at 60mph?

 

[KingNothing]

The fly is moving faster or slower relative to the ground, depending on the direction it's flying within the plane.

 

[Nyxie]

The fly is moving faster or slower relative to the ground, depending on the direction it's flying within the plane.

Yeah that's right.

 

[rcgldr]

If a fly(insect) flies from one end to the airplane to another, would it be flying faster than the airplane?

Note that "flying" implies the speed of something relative to the air it flies in, so with the way this question is worded, the answer would be no. So the frame of reference for the fly is the air inside the airplane, while the frame of reference for the airplane is the air surrounding the airplane. The fly is probably flying at around 5 mph in the air it flies in, while a commecial airplane flies at 350 mph to 500 mph or so in the air it flies in. If you start including frames of reference, there's the jet stream speed, the surface speed of the Earth as it rotates, the oribtal speed of the Earth around the sun, the orbital speed of the sun around the center of the Milky Way, ...

 

[Kaldanis]

Note that "flying" implies the speed of something relative to the air it flies in, so with the way this question is worded, the answer would be no. So the frame of reference for the fly is the air inside the airplane, while the frame of reference for the airplane is the air surrounding the airplane. The fly is probably flying at around 5 mph in the air it flies in, while a commecial airplane flies at 350 mph to 500 mph or so in the air it flies in. If you start including frames of reference, there's the jet stream speed, the surface speed of the Earth as it rotates, the oribtal speed of the Earth around the sun, the orbital speed of the sun around the center of the Milky Way, ...

I always wondered this. So if the fly could just hover in the middle of the aeroplane, would it continue to be pulled along at the speed of the aeroplane or would it eventually hit the end wall? Going on your reply I'd think the air inside the plane was moving at the same speed as the plane, so even if the fly just hovered there it would be carried along at the same speed?

 

[Nyxie]

Inertial reference frames aren't undergoing acceleration. Inertia: velocity doesn't change w/o outside force. Motion is measured relative to something else. So, if you're on a boat and you throw an apple in the air, it falls stright down since there wasn't a force acting on it (neglecting air friction or negligible forces). It's inertia hasn't changed.

Same thing happens on land, except on land the person on the boat who throws the apple looks like his apple is moving with him.
It's a consequence of inertia and the fact that only an external force can alter inertia. Your reference frame is inertial if it's not accelerating, otherwise if it's accelerating it "looks like" some force is pushing it the opposite direction of the acceleration.

 

[DaveC426913]

I always wondered this. So if the fly could just hover in the middle of the aeroplane, would it continue to be pulled along at the speed of the aeroplane or would it eventually hit the end wall? Going on your reply I'd think the air inside the plane was moving at the same speed as the plane, so even if the fly just hovered there it would be carried along at the same speed?

Yes. No need to overthink it: when you're in an airplane, you can't tell - by motion of air, or by motion of flies - that you're moving at all.

 

[Libohove90]

I always wondered this. So if the fly could just hover in the middle of the aeroplane, would it continue to be pulled along at the speed of the aeroplane or would it eventually hit the end wall? Going on your reply I'd think the air inside the plane was moving at the same speed as the plane, so even if the fly just hovered there it would be carried along at the same speed?

This is so important in physics. What you are thinking about has been thought by Galileo in the 16th Century. It is this analysis that has made Galileo formulate the concept of relative motion.

What you have to understand is that "all inertial frames of reference are on equal footing." The plane is an inertial frame (assuming its moving at a constant velocity in a straight line) and so is the surface of the Earth (approximately). There is no difference between the fly flying at 10 mph inside the plane or 10 mph relative to the surface of the Earth because they are both inertial frames of reference.

If the fly were to eventually hit the end wall of the plane, then that means one reference frame, the surface of the Earth, is more superior than the plane's reference frame. That is simply wrong. Motion is relative and all inertial frames of reference are on equal footing.