Pure maths, physics, logic (braingames.ru): non-trade-related brain games - page 118

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muallch: 1 This is true if the snow velocity is less than the speed of the cart. If the speed of the snow is equal to the speed of the cart, the total (cart + incoming snow) momentum will increase, but the speed will not.

What "it" is true? What are you talking about?

PS. If the snow falls on the cart naturally - falling from the sky - then naturally the speed of the cart will drop.
The rate of deceleration of the cart is determined by the rate of change in its momentum. And momentum is only lost when the snow is ejected (not counting friction, of course). When snow arrives from the sky, momentum does not change at all - regardless of snow speed.
 
Mathemat:

What "it" is true? What are you talking about?

The braking speed of a cart is determined by the rate of change in its momentum. And momentum is only lost when snow is ejected (not counting friction, of course). When snow comes in from the sky, momentum doesn't change at all - regardless of snow speed.
We seem to be talking about the same thing. Whensnow comes in from the sky, momentum doesn't change at all - regardless of snow velocity. I'm not arguing that! Impulse doesn't change, mass goes up, speed goes down. When snow is ejected, momentum and mass decrease, velocity does not.
 
muallch: When snow is thrown in from a nearby cart, mass and momentum increase, speed does not change.
It seems to be true.
 

When snow is thrown in from a nearby cart, mass and momentum increase, but speed does not change.

Sorry, I accidentally deleted this post - restored it.

 
muallch:

When snow is thrown from a nearby cart, mass and momentum increase and velocity does not change.

Accordingly, the reverse of the above action will not change speed either.
 
muallch:
_ When snow is thrown, momentum and mass are reduced, velocity is not.
Snow, when it falls from a shovel and hits the ground, what doesn't heat up from it and heat up the ground? Does it not have kinetic energy? If it does, where does it come from? Doesn't it come from the cart?
And if from the cart, then its velocity must be falling.
 

Dima, have a look at my solution, there are simple diphurcs (page 117). The law of conservation of energy is simply not needed there.

For speed - do not care, do not think about it. What matters is momentum, because it is its change that determines motion.

DmitriyN: Snow, when it falls from a shovel and hits the ground, what doesn't heat up from that and heat up the ground?
The heating/melting of the snow is not taken into account, this is explicitly stated in the comments to the problem.
 
Mathemat: _ The heating/melting of the snow is not taken into account, this is explicitly stated in the comments to the problem.
I get that, but the snow falling from the shovel has kinetic energy, I mean it has velocity in the direction of travel towards the cart. Where does that velocity come from? After all, before the snow fell on the cart, this velocity was zero. As it falls onto the cart, the snow acquires this velocity and therefore also acquires energy. And then, this energy is thrown out of the cart with the snow, so the energy of the cart thus becomes less, and therefore its speed also becomes less.
 
DmitriyN:
I get that, but snow falling from a shovel has kinetic energy, I mean it has velocity in the direction of travel towards the cart. Where does that velocity come from? After all, before the snow fell on the cart, this velocity was zero. As it falls onto the cart, the snow acquires this velocity and therefore also acquires energy. And then, this energy is thrown out of the cart with the snow, so the energy of the cart thus becomes less, and therefore its speed also becomes less.
And to put it simply: at the moment the snow comes off the shovel, the snow and the cart with the load go at the same original speed. The snow has taken away some of its mass and momentum and is flying separately. And what happens to it afterwards, the cart doesn't really care. If the snow only took away momentum, then the speed of the cart would decrease. But a body that takes away momentum but has no mass does not exist.
 
DmitriyN:
I get that, but snow falling from a shovel has kinetic energy, I mean it has velocity in the direction of travel towards the cart. Where does that velocity come from? After all, before the snow fell on the cart, this velocity was zero. As it falls onto the cart, the snow acquires this velocity and therefore also acquires energy. And then, this energy is thrown out of the cart with the snow, so the energy of the cart thus becomes less, and hence its speed becomes less as well.

So, understandably, the task is slowly being transformed. Soon there will be UFOs, aliens and the Flying Macaroni Monster.

P.S. Does anyone have any thoughts about a column of mega-mosks with hubcaps?

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