centripetal force

Zend

different stuff bor
if u can keep the angular velocity constant, that's uniform circular motion

and in this time, you wanna keep w constant but not v ar ma?
係一個高速盤中, 個w 係keep constant in every point

if w = constant , then F=mrw^2 = kr
if v = constant, then F= mv^2/r = k'/r

Puppet

原帖由 adamsteve 於 22-11-2008 23:43 發表
正如yu神所講  w 點會係constant 呢   v(magn ...

唔見佢有咁講

原帖由 Zend 於 22-11-2008 23:47 發表
different stuff bor
if u can keep the angular velocity constant, that's uniform circular motion

and in this time, you wanna keep w constant but not v ar ma?
係一個高速盤中, 個w 係keep constant i ...

我提議佢睇番angular velocity的定義 ω = θ / t

[S]【YU】

我無直接講出黎,不過唔可以話我無咁既意思.

instantaneous response =/= steady state response.

there are 2 processes in the whole picture.

if w = constant , then F=mrw^2 = kr
if v = constant, then F= mv^2/r = k'/r

both of them are true, but they are not used together in the same process.

[ 本帖最後由 [S]【YU】 於 23-11-2008 01:22 編輯 ]

piyopiyo

原帖由 [S]【YU】 於 23-11-2008 01:20 發表
我無直接講出黎,不過唔可以話我無咁既意思.

instantaneous response =/= steady state response.

there are 2 processes in the whole picture.


both of them are true, but they are not used together  ...

ic[[tk_02]]

Zend

其實ne 樣野new way係有講的~

piyopiyo

原帖由 Zend 於 23-11-2008 12:54 發表
其實ne 樣野new way係有講的~

邊樣野

Zend

原帖由 piyopiyo 於 23-11-2008 03:18 PM 發表
邊樣野

that particular thing

piyopiyo

原帖由 Zend 於 23-11-2008 16:53 發表

that particular thing

u mean Fc directly proportion to r?[[tk_27]] or u mean the illustration of why the man will move away the centre

adamsteve

我記得多數都係用返f=mv^2/r    係inversely proportional
v係constant架 yu神都有問你啦 舊野唔通會無啦啦愈行愈快咩

你地應該都係cut左angular momentum架啦 都好少用angular 野黎計
ω = θ / t   <--- 其實 同 ω = v/ r 係無分別ge 都可以拎黎用
你自己都可以試下拎去derive一下

你諗唔通 我諗你都係搞唔清楚個ω 係做緊咩姐 慢慢黎 抽離一下 唔好鑽牛角尖

Puppet

原帖由 adamsteve 於 26-11-2008 00:57 發表
我記得多數都係用返f=mv^2/r    係inversely proportional
v係constant架 yu神都有問你啦 舊野唔通會無啦啦愈行愈快咩

你地應該都係cut左angular momentum架啦 都好少用angular 野黎計
ω = θ / t   

Consider uniform circular motion (v is constant at a particular r).
Assume friction is always large enough (I don't know the mechanics of skidding).
Assume v is constant for all r (by 19#).

Since ω = v/r
As r increases, ω decreases.

ω = θ/t
v/r = θ/t
θ = k/r
In a particular time interval t, a body travels a larger θ if r is smaller.
Please imagine the picture if I places two bodies of the same mass at different r on the same rotating disc.

Actually do you know what the ω we are talking about??