Pure maths, physics, logic (braingames.ru): non-trade-related brain games - page 25
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A perfectly elastic ball bounces on a perfectly elastic surface with an amplitude of 1 cm. How can a brick thrown from a height of 1m be used to lift the ball to a height of 30m? (you can draw a picture)
Throw it on the same surface. And the ball doesn't have to be perfectly elastic, it can be a small brick.
OK, what then is an absolutely elastic collision?
- energy transfer to and from the surface is instantaneous
- The "spring" of the surface has an infinitely large k.
Throw it on the same surface.
It just won't work. I'm not asking for a drawing for nothing. And you have to do some math. It's a trick question.
- The "spring" of the surface has an infinitely large k.
This should be enough.
By the way, can you add problems there yourself?
(5 points).
On a plane on which a rectangular grid with a spacing of n is plotted, ink is poured in the form of many blots of different sizes and shapes. The total area of the ink spots is less than n². Prove that it is possible to shift the grid in such a way that no node of the grid is covered by ink.
The solution is very simple: I got the answer at the level of 6th-7th class of secondary (not physmath) school. The problem only seems complicated.
Mathemat:
TheXpert:
almost 25 cm, imho.
The first problem is correct. I told you that TheXpert is good at physics.
.................
I don't see an argument yet. It's just the usual conspiracy.
No, it will roll at almost exactly half the speed of ball 1. In the same direction.
I don't see an argument yet. There's the usual conspiracy.
Now explain why if this picture is placed vertically, the ball having twice the speed, will jump to a height four times higher.I join in. The fact that someone came up with a problem and his answer to it is not enough for me. The fact that the person who posted the problems liked the answer is not enough for me.
The proofs must be presented here and not in the form of a reference somewhere
OK, here's the solution. "Credit" doesn't mean that the reasoning is guaranteed to be correct, but the answer is definitely correct.
The "lots of letters at the top" has already been nicely cleared up in two ways. And the basic question is inarticulately jammed at the end.
Since the brick bounces upwards almost at the speed of falling on the spring (it reaches almost the same height as at 1 m), the spring (ball) will therefore bounce to a height equal to almost a quarter of the height of 1 m, i.e. almost 25 cm.
Anyway, I had to do my own investigation. I managed to find out that the conspiracy seems to be worldwide. All over the internet this wild formula: S = V^2/2g
Which really means that a body tossed with twice the speed will supposedly jump to four times the height.
How to live in this crazy world?
Go shoot yourself...
And the main question is inarticulately obscured at the end.
Anyway, I had to do my own investigation. I managed to find out that the conspiracy seems to be worldwide. All over the internet is this wild formula: S = V^2/2g
Which really means that a body thrown up at twice the speed will supposedly jump to four times the height.
What's so wild about it? The usual Newtonian conspiracy. That's not the gimmick, it's that you have to look at the spring as a whole body.
And what's the inarticulate question at the end?
By the way, the cue ball example is not very correct. They don't just move - they roll. They have two kinds of kinetic energy - translational and rotational.