# Ball physics question

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Hi,

I have a simple (probably) math problem but I'm not very good at math. My question is if there's a ball that initially rises 2 meters per second upwards and the rising slows down one meter on each second, how long it takes for the ball to stop rising?

formula for this would be nice!

thanks!

Edited by heh65532

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Is this homework?

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Quote

the rising slows down one meter on each second

Hi, you're describing a motion with constant acceleration:
acc = - 1 m/s² (per second "squared" because the change of velocity is acc m/s, per s)

The velocity is the integral of the acceleration over time, here:
vel = acc * t + vel0 m/s, because acc is constant, and where vel0 is the initial velocity

So the answer to your question is the solution to acc * t + vel0 = 0 which yields t = -2 m/s / -1 m/s² = 2 s

Edited by D.C.Elington

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28 minutes ago, Lactose said:

Is this homework?

no

26 minutes ago, D.C.Elington said:

Hi, you're describing a motion with constant acceleration:
acc = - 1 m/s² (per second "squared" because the change of velocity is acc m/s, per s)

The velocity is the integral of the acceleration over time, here:
vel = acc * t + vel0 m/s, because acc is constant, and where vel0 is the initial velocity

So the answer to your question is the solution to acc * t + vel0 = 0 which yields ﻿t = -2 m/s / -1 m/s² = 2 s

That's a correct result (2s), thanks. But sorry if I'm just not getting it but I need the formula for t

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That would be " t_stop = - initial_velocity / acceleration "

Quote

sorry if I'm just not getting it

No reason to be sorry! Incidentally this part of maths dealing with equations is called "algebra".

Edited by D.C.Elington

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@D.C.Elington thanks! I can't believe the answer was so simple

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As a rule of thumb when you try relate a quantity and its rate-of-change you can expect a simple relation!
Here the acceleration is actually the rate of velocity change as you said it yourself.

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It's worth mentioning the SUVAT equations. They tell you all kinds of things about projectile motion!

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On 9/24/2019 at 11:33 AM, taby said:

It's worth mentioning the SUVAT equations. They tell you all kinds of things about projectile motion!

It's probably worth learning enough calculus that you can derive everything yourself from just knowing that velocity is the derivative of position and acceleration is the derivative of velocity. I literally don't remember any of the formulas, but I don't need them.

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Didn't someone say that those who can't do calculus, do numerical analysis instead? That's why I use numerical integration, like the 4th-order symplectic integration code that I got from you a while back. I'm horrible at calculus.

Edited by taby

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