Why don't we move backwards when we jump in a car?
473407
An object in motion remains in motion unless it is acted upon by an outside force.  Say you're traveling in a train going 200 miles an hour, jumping on a trampoline.  Before you jump, both you and the train are moving 200 miles an hour forward.  When you jump, you'll begin moving upward at about 5 mph, but you'll still be going 200 mph forward as well, just like the train.  When you come back down, you'll meet the trampoline exactly where you left, because you, the train, and the trampoline have all been moving forward at the exact same speed.  Here's another example:  The circumference of the earth is around 24,000 miles, and the earth completes one revolution per day.  That means that, in one day, you travel in a 24,000 mile circle, yet you don't feel that you are moving because everything else is moving at the exact same speed.
1125526
No, they can move to the sides or backwards, but cannot move forward.
135305
YES!  It's perfectly possible to _build_ such a car.  If the magnet is just attracting the car, it would pull forward on the car, and the car would pull back on the magnet.  Nothing moves.  If the magnet is attracted to an object ahead, the rig would move forward but would stop when the magnet got there.
971235
Depends on your momentum when you do so.\n\nIf you're utterly still and blow out air in space, you will move backwards.\n\nWell, your frozen corpse will...
114124
Probably the simpliest way I can think of is just to strap the balloon to a set of wheels and position it so that the opening is point in the opposite direction you want the car to move.  When the balloon is released, the air can escape out the hole and propell the car forward.
61716
The air inside the vehicle is moving the same speed as the vehicle. To the fly it's still air, unless a window is open, then the fly may not be able to fly normally.
188819
Air inside the car is travelling at the same speed as the car. So for a fly, the car is not moving.\n\nThe Earths rotates at a speed of 1000 miles/h at the equator. If you jump why don't you fall miles away? The answer is the same, the Earth is the car and you are the fly.
792554
This is a great question and has real potential. Yes, it's true that the earth doe's indeed move beneath you even though you won't see or notice it. I jumped and timed myself and found that my time in the air was .5 sec. I tried to start and stop my stop watch as fast as I could and could only do it in .17 sec. Yours was really a fast jump. When jumping you increase the distance of your orbit from the center of the earth, so to land exactly back in the same point, you need a slight increase in speed going up and decrease coming down and only this would satisfy no earth movement beneath you when you jumped, providing that you jumped in the same direction as the earth's rotation. The speed calculations decease as you get closer to the north or south pole.
44366
einstein's theory of relativity.  in the frame of reference of the car, you are stationary, the fly is stationary, and everything else in the car or moving with the car is stationary. this is why if you are in a car and drop a book onto the seat, it goes straight down, not toward the back. it is going at the same speed as the car and therefore is still relative to the car. there is no force acting on it to make it behave otherwise.  that's why you don't feel anything in a car unless you're accelerating or decelerating. so you feel like you're pushed forward when the car is coming to a sudden stop. because then there's a force stopping the car, and therefore you, so you feel it. in this case, the fly would also go flying(no pun intended) to the front of the car.\n\nif this is still unclear, think of the earth. the earth is rotating with a speed of over 1000 m/s, but you don't feel it. that's because you're moving at that same speed, you're stationary relative to the earth so you feel stationary because your frame of reference is the earth.
284269
I am sure someone cleverer will come along and shoot holes in this but I think this has a lot to do with Newton's 3 Laws (Newton being a clever dead bloke).\n\nForce: When you kick your sister in the shin you are using force\nMass: If she is fat, she has lots of mass\nInertia: Being fat, she will not be able to chase you. She has inertia. \n( Example from - http://www.allworldknowledge.com/newton/index.html)\n\nSo you are on the train and you are moving - its worth remembering that gravity (the force which keeps you on the floor) only goes downward not along. You on the train are moving along and the 'force' of the train going along, keeps you going along. Get it?\n\nWell you're still going along, watching the world go by, and then you jump.\n\nBy jumping you're still going along with the direction of the train thats one force. But when you start coming down it's the gravity pulling you back, as another force. The train moving you along hasn't changed, you just have two forces one pulling you down (the jump) and one pulling you along (the train).\n\nSo you end up in exactly the same place. With a few miserable commuters.
1087367
When the car is traveling at 100 mph, everything at rest with in the car is also traveling at 100 mph, this includes you, the air, any any flies present.\n\nWhen you suddenly stop the car, you are not just stopping the car bu also everything inside as well.\nPretty much everything within the car slows down/stops at the same rate (assuming ample "Stopping" forces).  So when you step on the brakes, the fly slows down too, despite the fact that it is not physically connected [strapped down] with the car.\nThe fly does not slam into the windshield for the same reason the back of the car does not turn into a vacuum.\n\n\nEDIT:\n"memento mori", inertia would be a reason why the fly might indeed hit the windshield, not why it might not.\nInterial is the property of matter which says that objects tend to continue doing what they are doing (objects at rest stay at rest, objects in motion stay in motion, ...Newton's 1st law).\nIf the fly was in motion and you slammed on the breaks, the fly should stay in motion, not come to a rest.....unless of course, something did work on the fly (applied a "stopping" force over a distance) in order to change its kinetic energy.
707613
Some good examples are shown at http://www.cape.k12.mo.us/cjhs/science/strom/newton's_laws.htm.\n\nThe core of the problem is well described by:\n"Your vehicle must use Newton’s third law of motion to move forward; it must move forward by pushing backward on the floor, the air, or some other object."\n\nI frequently see the rule that electricity may not be used, though this seems to be inconsistent since electricity is just another form of stored energy and you still have to apply Newton's 3rd law to make your scooter move.\n\nAnyway, your problem is to store up sufficient energy somehow and then to release it in a controlled manner so that your scooter makes the 1.5M distance without crashing into the far side of the room. The simplest way to do this is through a spring of some kind. One good source for a spring would be a common mousetrap or rat trap. The mousetrap has a torsion spring that is loaded with energy when you set the trap and which suddenly releases it's energy when the trap is sprung. Some examples are shown at http://www.hypography.com/topics/mousetrapcar.cfm and http://www.docfizzix.com/how_work.htm (really good instruction site).\n\nAnother way to store energy in a spring is to blow up a balloon. The air inside the balloon is forced out and can propel a car. See http://www.balloonhq.com/balloon_car/balloon_car.html for some ideas.\n\nIn either case, you need to have some control over your energy release. With the mousetrap, the size of the axle and the wheels are important, as they determine the "gearing" of the energy transfer from the mousetrap to the floor. For the balloon, you'll want some way to experiment with different size nozzles to control how fast the air is released.\n\nYou can find wooden wheels at arts and crafts stores. You'll need something for an axle that turns smoothly or you'll lose all of your energy to friction.\n\nI'd go with the moustrap car shown on http://www.docfizzix.com/how_work.htm\n\nGood luck!
779439
Friction helps wheels to move the car forward (and to push the earth behind). If not friction, the wheels would rotate, and the car would stay without motion.
239154
WOW! Why don't you cross in the opposite direction and stay.
482200
Because when a person steps forward, their stride is longer from years of experience and balance.  When you try to step back, you are stepping blindly...(unless you have eyes in the back of your head) or turn your head around.  The body is more cautious stepping back for saftey reasons, therefore, the steps in reverse are smaller.  As a result it takes more smaller steps to undo less larger steps.  It is usually more difficult to undo things than it is to do them...Take the toothpase analogy for example...it's easier to squeeze it out than to put it back in the tube.
76756
absolutely. Think of it in terms of cruise control. you are moving in your car at a continuous speed of 60 mph. Acceleration means increase of speed, deceleration is decrease of speed. However, a car at continuous speed would have the acceleration of zero.
541091
Inertia means two things:\n\nAn object at rest will stay at rest, unless another force acts on it.\n\nAn object in motion will continue in motion, unless another force acts on it.\n\nAny force which changes the motion of an object -- the speed and/or direction -- is called acceleration.\n\n...You're riding along in your car.  Both you and the car have inertia; that is, you're both in motion, and will continue to move until something changes that.\n\nThe car runs into a wall, which certainly makes a big change in the car's motion.  You, on the other hand, and anything else inside the car that wasn't strapped down, will continue to move forward because of your own inertia.  Without a seat belt or air bag, your body will continue to move forward through the windshield, which is undignified, extremely painful, usually fatal, and a big drag to clean up.\n\nSo:\n\nA)  Seatbelts put you more "in contact" with the car; which is to say, any force which affects the inertia of the car will be more efficiently transferred to your body -- though not *so* efficiently that you go "splat" like the rest of the car; they just restrain you from continuing forward into the windshield.\n\nB)  A head rest acts as an accelerator for your head.  If the car accelerates suddenly (such as when somebody runs into the back of your car), the car's seat transfers that acceleration to your body.  The head rest acts as an extension of the seat, so that your head is also accelerated and doesn't get "left behind" because of its own inertia.\n\nC)  In practical terms, a force which is applied directly opposite to an object's direction of movement is called "deceleration."  It's still the same thing as acceleration, but we treat it as if the speed an object is going in a particular direction is being decreased in the same direction.  When the car hits the wall, as your body's inertia propels you forward, the air bag acts as resistance to that forward movement, decelerating the forward motion of your body.\n\nThe point to all three of these is to gently transfer acceleration to your body.  A car is much more rigid than your body (for instance, if you were to accelerate really hard, the rear bumper isn't going to get left behind), and is able to take much more drastic changes in its speed and direction.  Your body is much more fragile (and much more valuable) than a car, so seat belts, head rests and air bags are used to ease the changes in acceleration.\n\nAs you know, falling off a tall building isn't what kills you, it's the big fat splat at the bottom.  When you fall, your body accelerates down with a force of one G (which stands for earth's gravity), which your body can handle quite well.  But when you hit the ground, the ground acts to accelerate you in the opposite direction (up) *very* quickly, with much more acceleration than your body can stand.  If there's a big enough air bag to land on, it will slow down the up-acceleration (or down-deceleration, whichever way you look at it) to something that your body can handle.  Now, turn the whole setup sideways, and that's the reason for seatbelts, air bags and head rests.