主要區別-速度與加速度

速度和加速度都是與物體運動有關的向量。速度和加速度的主要區別是速度是位移的變化率，加速度是速度的變化率。

什麼是速度(velocity)？

If the position of a body can be represented by a position vector  , then the velocity of the body is defined as:

這給出了物體的瞬時速度，即在特定時間的速度。平均速度由下式給出：

速度是物體速度的大小。平均速度是身體行駛的總距離除以所用的時間。如果一個物體移動一段距離，回到它的起點，物體會有一個平均速度，但它的平均速度是0，因為它的位移是0。因為速度是一個向量，速度的變化涉及到物體速度的變化或運動方向的變化。

These cars are accelerating since they are changing their direction of motion even though their speed may remain the same.

測量速度的國際單位制是ms-1。

什麼是加快(acceleration)？

加速度定義為速度變化率：

根據牛頓第二運動定律，產生加速度需要合力。如果加速方向與身體運動方向相反，則身體處於減速狀態，速度降低。

測量加速度的國際單位是ms-2。

Bodies falling under gravity close to Earth’s surface are approximately falling at a c***tant acceleration of about 9.81 m s-2. This acceleration is given the symbol . Sometimes,  is used as a unit to express acceleration. If a human is exposed to an acceleration higher than about  , blood may not flow into the brain the person might lose c***ciousness. This can happen, for example, in roller-coasters achieving high accelerati***. Astronauts and aviators need to be trained to stay c***cious at high- accelerati***. The video below shows a trainee losing c***ciousness from an acceleration of   (Note: GLOC stands for “-induced Loss Of C***ciousness”).

速度(velocity)和加快(acceleration)的區別

定義

Velocity is the rate of change of displacement:  .

Acceleration is the rate of change of velocity:  .

單位

速度單位為m s-1。

加速度單位為m s-2。

Image Courtesy:

“ Fontana, Calif. (May 1, 2004) – The U.S. Navy sp***ored Chevy Monte Carlo NASCAR…” by Chief Journalist Erik Schneider. (U.S. Navy photo ID 040501-N-1336S-037) [Public domain], via Wikimedia Comm***