If you jump in a lift that is moving downwards, how come you dont hit your head?

Question

Or if you are on a roof of a moving train and try to jump onto the carriage in front - why don't you end up landing further back?

Answer 1

Because you are already travelling downwards at the same velocity as the lift.  

It's like throwing a tennis ball in the air in a car that's driving.  It doesn't fly through the rear window because the ball already has the forward velocity of the car.  

Answer 2

you are so thick

Answer 3

Because despite your jumping upward, you are still moving downward at the same rate of speed as the lift.

Answer 4

When you are on a moving train, you are moving with the same velocity as the train relative to the ground, even though it feels like you're still.  You are moving at a constant velocity, and aren't accelerating.  Relative to the train, you're not moving at all, because you are both moving the same speed in the same direction.

When you jump, the only thing that changes is the train's floor is no longer pressing up on you.  Before you jumped, the train wasn't pushing you forward, only upward.  It only pushes you forward when it accelerates.  You were already moving forward at say, 50 mph before you jumped.  When you jump into the air, you're still moving 50mph forward, you don't need to keep getting pushed to maintain the speed.

A good analogy is throwing a baseball.  Your hand pushes the ball to reach a certain speed, then once it reaches a fast speed, the hand lets go of the ball.  The ball keeps moving at the same speed your hand was moving.  

Now, imagine this: you release the ball, but keep moving your hand right next to it (either you have very long arms or are a very fast runner).  This is what the train is doing with you.  When you jumped, the train "let go" of you, but you kept the speed.  But after it let go of you, it kept following you, like your hand kept following the ball.  Just like the ball won't fly behind your hand, you won't fly backwards on the train.

And you don't need to worry about air resistance because you're not moving through the air, only the train is.  The air inside the train isn't blowing backwards.

But if you were to jump out the train window, THEN you'd land further back, but not by a whole lot.

As for the elevator, it's the same concept.  When the elevator is moving down at a certain speed, so are you.  When you jump, you're not actually moving upward.  You're still moving downward, just a little slower than the elevator, so the net result is that you're moving upward RELATIVE to the elevator.  But only fast enough to get a couple feet in the air before accelerating back down.

If you're wondering how you catch up to the elevator floor after jumping, remember the elevator isn't accelerating, it's moving down at a constant speed.  When you jump, however, you are no longer being supported by the floor, so you begin to accelerate down.

I hope this doesn't sound confusing, it's a simple but important concept

Answer 5

maybe the gravity is just as fast as the moving object

Answer 6

the lift - becos its moving down, you dont jump with the force you would on a solid surface.

the train - becos the train is moving in the same direction you are trying to jump, it gives you more momentum (opposite to the lift scenario).

Answer 7

In the case of the elevator you are falling faster than the elevator. When you jump on a moving object, the motion of the moving object is built into your motion, the effect is the same as jumping on a stationary object.

Answer 8

This is because when you are in a lift your acceleration in the downward direction is same as that of the lift. So when you jump up it is like jumping anywhere else.

As a matter of fact you are moving along with the Earth although your position seems stationary to you.

If you were to imagine that the Earth were to stop spinning , we would all fly out due to our inertia of moment.  

Answer 9

I think you are forgetting that once the lift starts moving or on the moving train...you are in motion as well. For the lift to have the effect you are thinking it might have, it would have to descend at a rate commiserate with the speed of a free-falling object (32 feet per second/per second) then you too would be in free fall. As it is, after a micro-second of decreased gravitational effect following the lift starting downwards (and you will notice, I said decreased gravity...not NO gravity.), you body catches up and is also in motion just as the lift is...This means that any action you take is taken with that forward/downward or whatever direction motion in effect on you as well. Does that explain it in a way that is more comprehensible? By the way...if you jump straight up on the train, and can stay in the air long enough that your forward momentum has time to decay, you WILL see an appreciable difference in your landing spot from a similar stationary jump.

Answer 10

This is because when you are in a lift as the lift goes downwards the downward force acts on you and due to this downward force you are attracted towards the base of the lift so even if you jump you dont hit your head

2. when you travelling in a train the force in the opposite direction to what the train is moving attracted you or keeps you attached to it do you dont fall directly in the carriage but move more back

Answer 11

You are the lift are moving at the same rate. In order to hit your head, you would have to jump high enough to hit it if you and the lift were standing still. You are the lift are not moving relative to one another, so it's like both things are standing still.

If you're standing on the roof of a train (lets ignore friction with the air for now) then again, you and the train are moving at the same rate, so it's as if both you and the train are standing still. If you jump forward, you will move forward as would normally be expected.

Answer 12

The lift: if you jump hard enough you can hit your head on the ceiling, the problem is with jumping hard enough to overcome your own rate of free fall.

The train: it's because of inertia. When you stand in a moving train, you and the air around you move at exactly the same speed and direction as the train. When you jump, it makes no difference to that movement, the inertia still keeps you going in the direction of the train.

Answer 13

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Answer 14

Because when you jump, you change your speed relative to the speed you were already moving. For example, if you were able to jump at 2m/s upwards normally, and were in a lift travelling at 3m/s downwards, you would have a speed of 1m/s downwards relative to the ground.