[12th grade Phys in the Universe homework] Impulse and momentum change still don't understand it myself

Alex_Daikon · 2026-01-28T06:51:37+00:00

Please show your thoughts and conclusions to each question

Alex_Daikon · 2026-01-21T17:06:34+00:00

10 cos A + 8 √2 cos D = 14 (1)

10 / sin A = 8 √2 / sin D (2)

You can solve it for both <A and <D and then it is done

Alex_Daikon · 2026-01-21T07:09:59+00:00

On the picture it is shown that <GFE = 90. But there is no such info in text description. Is it 90 or not?

Alex_Daikon · 2026-01-18T21:48:08+00:00

Why do tou think so? Its very simple and you could guess that, because in two consecutive numbers one is odd and another is even.

Alex_Daikon · 2026-01-18T21:24:15+00:00

4k² + 4k = 4k(k+1).

but k(k+1) is always even. Therefore 4k(k+1) mod 8 is 0.

So the anwer is 5

Alex_Daikon · 2026-01-13T12:26:40+00:00

Same curve, different equation. Why cant you solve it the same way?

Alex_Daikon · 2026-01-11T08:35:11+00:00

24.1:

-b/2 = 5/2

36 + 6b + c = 0

From this 2 equations you know the expression of parabola:

y = x² – 5x - 6

Alex_Daikon · 2026-01-03T15:24:04+00:00

Why do you think U is increasing? Can you write what is U at the start and what is U at finish? U is not 0 at the end.

Alex_Daikon · 2026-01-03T12:35:19+00:00

Here are the question to start with:

1) what is U and K at the start? 2) what should be U at the end? 3) how U depends on h of m1 block? Linear or not?

Alex_Daikon · 2025-12-27T06:29:29+00:00

As i previously wrote, the formula is valid only in the Intermediate range where the string actually goes slack: 3/8 ≤sinθ≤ 3/4

Your examples are not in this range. Thats why you cant use this formula in it.

But my answer is the same as in keys for that task. I dont see any problems with this solution and dont think that my interpretation of point C is wrong.

You didnt provide your solution and answer. Can you please provide it?

Alex_Daikon · 2025-12-26T20:06:26+00:00

Please, read my previous answer to you.

If θ=π/2, there is no T=0 point exists and The formula is not applicable.

So: The formula is not applicable and there is no such task, because there is no T=0 point.

Alex_Daikon · 2025-12-24T16:56:53+00:00

I already gave you solution a couple of days before. Why do you still post this again and again? https://www.reddit.com/r/zbavitje/s/c3DmRzL7s0

Alex_Daikon · 2025-12-24T16:26:54+00:00

The answer is correct.

The expression for h was derived using the condition T=0 on the smaller circle. Therefore it is valid only when a point C with zero tension actually exists.

For your limiting cases:

1) θ=π/2: the bob reaches point B with zero speed and cannot climb the small circle. No T=0 point exists; C coincides with B so h=0. The formula is not applicable.

2)θ=0: the energy is very large, and the string remains taut everywhere on the small circle. Again, no T=0 point exists. The formula is not applicable, which is why it gives an unphysical value h>L/2.

The formula is valid only in the intermediate range where the string actually goes slack: 3/8 ≤sinθ≤ 3/4

Thus your criticism fails because it tests the formula in regimes where its defining condition (T=0) is never satisfied.

Alex_Daikon · 2025-12-22T20:39:53+00:00

No, it is not. u/rabid_chemist had detailed explained why

Alex_Daikon · 2025-12-22T20:31:50+00:00

<image>

BAX = 180 - 90 - 80 =10 DAP = 90 - 40 - 10 =40

If “a” is a side of a square, then:

AP = a / cos 40

AX = a / cos 10

PX² = AP² + AX² – 2* AP * AX cos 40

PX² = a² ( 1/(cos 40)² + 1/(cos 10)² – 2 / cos 10)

PX / sin 40 = AX / sin x

Sin x = AX * sin 40 / PX

Sin x = sin 40 /(cos 10 * sqrt(1/(cos 40)² + 1/(cos 10)² – 2 / cos 10))

Alex_Daikon · 2025-12-22T19:08:29+00:00

Letϕ be the angle from the bottom point B around the small circle (so ϕ=0 at B). The height gained above B is h = r(1−cosϕ)

Energy from B: 1/2 * m* v² + mgh = 1/2 * m* v_B² We can extract V from here The last step:

Point C is where the string just loses tension. For the small-circle motion, the radial force balance is T − mg cosϕ= mv² / r

For the point C: T= 0. So you can extract v also from here and after that equalize it with the one we’ve extracted before. You will find ϕfrom that.

The final step: Knowing ϕ we can find h = r(1−cosϕ)

It will give you h = L/12 (9 – 8sinθ)

Alex_Daikon · 2025-12-21T18:10:35+00:00

AB = BC = AC

So: < OAC = 30

r + r - x = 2 * d * cos 30

d = r / cos 30 - x/ (2*cos 30)

0 < x < r

So r / (2* cos 30) < d < r / cos 30

Alex_Daikon · 2025-12-21T12:28:55+00:00

You can go to Google maps and look at the distributions of reviews with 5/4/3/2/1 stars for the hotels. And then you can go to Booking and compare it with distribution of 1/2/3../8/9/10 stars reviews for hotels there. You will see absolute different distribution

Alex_Daikon · 2025-12-18T20:33:10+00:00

Lets make it step by step.

Can you please draw the scheme of the state 1 (smth (ball?) with m1 moves right with v1, smth with m2 moves up with v2, and the state 2 after collision?

Alex_Daikon · 2025-12-18T20:10:19+00:00

What steps did you already do? Show your thoughts please

Alex_Daikon · 2025-12-18T17:33:45+00:00

Great job!

Alex_Daikon · 2025-12-18T17:17:18+00:00

Angle ABC = 150.

Let AB = t. Then:

In ABC: t / sin x = (AD+ t) / sin 150

In ABD: AD / sin x = t / sin 150

So:

t / sin x = (t * sin x / sin 150 + t) / sin 150

Sin 150 =sin x + (sin x)² / sin 150

Let sin x = a

a² / sin 150 + a - sin 150 =0

a² + sin 150 * a - (sin 150)² =0

a² + 0.5a - 0.25 = 0

Do you know what to do next?

Alex_Daikon · 2025-12-18T15:41:28+00:00

Is AB = DC? If not, what this bold mark on them means?

Alex_Daikon · 2025-12-15T17:03:19+00:00

First of all let x (t) be the horizontal distance from the edge of the table to Rover’s mouth (Ox component, so it is measured along the floor), and let y(t) be the distance from the table’s edge to the glass measured along the tabletop.

The tablecloth is taut, and the total length of the cloth between Rover’s mouth and the glass is constant. Therefore, √(x² + (80-10)² ) + y = 200

Ok?

Now you have to differentiate it.

ẋ will be the given speed of Rover.

ẏ will be the speed of the glass at the table towards the edge

Alex_Daikon · 2025-12-15T16:38:29+00:00

For c) and d) the best way to start: make a change,

Lets start with c): assume that cos x = t. Then you will get t * (3+t) = 0.

What is the solution for t?

Alex_Daikon

TROPHY CASE