A complex question on physics and sport?

Question

Whilst watching the olympics and other various athletics events I have always pondered this question: If the Earth spins on its axis at a high rate (I presume it must be at leat a few metres per second), why if a long jumper jumps against the direction the earth is spinning doesnt he jump out of the stadium! Or if he jumps in the direction the earth is spinning doesn't he travel backwards? If anyone has a simple explanation other than just one word - 'gravity' then I would like to hear it!

Answer 1

it is all about perspectives and Galilean transformations. imagine you are in a train, when you drop a ball in front of you, it lands in front of you instead of landing at the back. but to an observer standing outside the train, the ball move in a parabolic trajectory.

now the train becomes the earth and therefore the earths movement won;t affect the distance a long jumper jumped relative to a stationary observer on earth.

we don't feel the earth moving because the earth is rotating in a constant speed, according to one of the postulates in special relativity, the laws of physics are the same in all refernce frames.

Answer 2

Jared Z has the right idea. Sorry to say that the other answers above are wrong. We are "coupled" to the rotating Earth and have a velocity that is non-zero in everything we do, even standing still. When we jump, we add or subtract a little from that much larger baseline motion and it is only the small difference that we observe. Even on an asteroid that would be true (assuming it's gravity was strong enough to pull us back down) because it isn't the wind dragging us along, it is our motion before we jump that is in synch with the surface.

Aloha

Answer 3

OK I'm going to answer your question with another question. what happens if you are travelling on a bus and you throw a straight ball up in the air? why it lands back in your lap of course i hear you cry and of course it does.

the reason it does this is because no force has been acting on it to slow it down (apart from air resistance which is small so we can ignore it) so it continues to travel at the same rate as it was when you were holding it.

this is exactly the same in the case of your long jumper. he continues to travel at the rate the planet was spinning only this time there is a small force on him (his jump) however this lacks the force to move him far before gravity pulls him back down to earth. i hope this has helped

as an interesting side note if you were to travel fast enough doing the long jump (and i mean really fast) it would be possible to travel right round the world as the ground would be falling as fast as you did anyway

Answer 4

At the equator the circumference of the earth is about 40,000km.
This means that the speed of the surface is about 463m/S moving from west to east.

Note, the speed of sound in air is about 340m/S at sea level.

If you throw a ball to a friend, lets say in the same direction as the rotation of the earth, it does not create a loud bang as it goes through the sound barrier and then a loud squelch as it drives a hole through your friend' chest! Here is why........

Just before you throw the ball, you, your friend, the air, the earth's surface and the ball are moving towards the east at 463m/S. Relative to each other, all these objects appear to be stationary (for the sake of argument it is a windless day).

At the moment that you throw the ball, everything remains the same except that the ball has a bit of extra speed (v) and so is moving towards the east at (463 + v)m/S. It's speed is, of course, only vm/S relative to everything and everyone else.

At this point, logic would have the ball moving in a straight line while you, your friend and the earth's surface move in a curve. This would result in the ball climbing in altitude relative to the earth' surface and passing over your friend's head. This does not happen because the ball is subject to the acceleration towards the earth's center that is also keeping you and your friend on the ground (gravity).

A similar thing happens if your friend throws the ball back to you.
It has just occurred to me that if I had used your brother in place of your friend, I could, at this point, have said that it is all relative!

Answer 5

As people have said, it's to do with momentum. You are always moving with the Earth (as is the atmosphere). When you jump straight upwards the Earth moves round, as it is spinning BUT you also move round, because nothing has stopped you moving round with the Earth, so you land in the same place you started.

So to apply this to long jumpers: when they jump they move relative to the Earth, so whichever way the long jumper faces, he will jump the same distance (apart from variables like wind speed, different run up speed, differnt take off power, and angle etc.)

Answer 6

The reason is not directly concerned with gravity or with the earth's atmosphere at all. The long jumper is already moving with the earth before he/she jumps. The jump moves the athlete in relation to the earth.

Answer 7

Relativity

In other words we are travelling with the Earth.

If you could jump faster than the spin of the Earth then you would make a world record!. but we know that's impossible.

By the way, that's why the space shuttle can leave the planet because it travels faster than the Earth.

Answer 8

You take the horizontal velocity of whatever you jump off. So as we are standing on what he jumped off it looks like he doesn't have any forward velocity at all. Same responce if you asked what would happen if you jumped up and down on a train. You always land in the same spot if the train keeps to the same speed. The earth does not change speed either.

Answer 9

The earth rotates once every 24hrs. It goes around the sun once a year
the rate of spin some say is 1800 miles an hour. You are spining at that same speed with your feet on the ground. The part that gravity plays is that you are positioned to jump in the air for a short period of time ie the power of you own strenght to push against gravity to lift you off the ground. Because of the power of yourself and gravity you can only be off the ground for no more then a second. In that time of being in the air, wind, atmosphere and gravity put you in a travelling motion thus it doesnt matter which way you jump this will always end up in landing in virtually the same position. If the wind is stonger it will carry you futher. and yes once you leave the ground you are travelling 4 times the speed of sound

Answer 10

Because the athlete and everyone else is also spinning with the Earth. Just like when you are in an airplane, you are moving 600 miles per hour with the plain, yet, when you move about the plane nothing unusual happens.