# Mosquito in a Bus [duplicate]

This question already has an answer here:

My Question goes like this: If a mosquito inside the bus wants to move from back to front, will there be any difference if the bus is stationary or moving (ie extra effort in the latter case?)? Consider it as a closed bus & mosquito at a fixed point in bus, ie the air column will be constant throughout the process, & the mosquito will always be in that air column & never touch any part of the bus.

Here's another question which has the similar answer as above question : Suppose the bus is at rest, & mosquito is also at rest (wrt to both ground & bus) and is in the air column, & not touching any part of bus. If bus starts moving, will the mosquito stay at rest wrt ground, ie go to back, or will it stay at rest wrt bus?

For both questions, consider that when bus starts,it instaneously starts moving in constant velocity.(no acceleration)

Thanks in advance to everyone who tries to answer it.

## marked as duplicate by jinawee, Kyle Kanos, Brandon Enright, Abhimanyu Pallavi Sudhir, John RennieJan 19 '14 at 7:03

Small insects and animals have to deal with the viscosity of the air. The motion of the train takes the air with it, the air does not accumulate at the back neither during acceleration or steady velocity. The effect will be small and only during acceleration. The air has the steady velocity of the vehicle and anything suspended in it by buoyancy will have the same velocity

It is easier to see with water , which will slosh initially backwards during acceleration, and at steady velocity will have the velocity of the container, which is in contact with the vehicle.

We feel the effect of acceleration in a car by being pushed back in our seats at start up, and falling forward at slow down, and the mosquito will feel a bit of this, cushioned by the viscosity of the air. At steady velocities it is as if we are sitting at the table at home and the mosquito will also be motionless with respect to the vehicle and us.

• Alright.My main doubt was in the fact that mosquito & bus are never in contact.but the air being in contact with both,the effect of motion gets to mosquito via the air...Did I understand correctly ? – Sumedh Jan 18 '14 at 16:04
• yes, with some delay during acceleration . – anna v Jan 18 '14 at 16:18
• Your answer is incorrect - water is far more viscous than air, and a mosquito is still a relatively large object (compared to a virus). We are pushed back in our seat, because we are in contact with the seat when the car is moving. The mosquito is not in contact with the car, just some of the air particles in the car (which may or may not be in contact with the car, depending on the air pressure). As the pressure tends to towards a vacuum, it is less likely that air particles will be in contact with the mosquito or the car, and in a perfect vacuum, the mosquito will crash into the shield.. – Kaizer Sozay Jun 7 '17 at 11:44
• Although a mosquito will probably die in a vacuum making the answer pointless, but your answer really should highlight how the behaviour changes with air pressure in the bus. – Kaizer Sozay Jun 7 '17 at 11:49

Using Galileo's Ship as an example:

"Shut yourself up with some friend in the main cabin below decks on some large ship, and have with you there some flies, butterflies, and other small flying animals. Have a large bowl of water with some fish in it; hang up a bottle that empties drop by drop into a wide vessel beneath it. With the ship standing still, observe carefully how the little animals fly with equal speed to all sides of the cabin. The sh swim indi erently in all directions; the drops fall into the vessel beneath; and, in throwing something to your friend, you need throw it no more strongly in one direction than another, the distances being equal; jumping with your feet together, you pass equal spaces in every direction. When you have observed all these things carefully (though doubtless when the ship is standing still everything must happen in this way), have the ship proceed with any speed you like, so long as the motion is uniform and not fluctuating this way and that. You will discover not the least change in all the insects named, nor could you tell from any of them whether the ship was moving or standing still."

I would think the same would apply to the mosquito, the mosquito would move with the bus, relative to it, not taking any extra force to move from the front to the back of the bus regardless of whether it is moving or not.

That's just my opinion, but I am a meagre student who's just touching on the concept of relativity!

If the mosquito is in the bus and it moves with no acceleration there is no question of an extra effort in the latter case. For the 2nd question it always stays at rest wrt bus, as it is in the frame of the bus.