phy_2.9_circular motion 圓周運動 2

物體作勻速圓周運動時，它的速度

When an object performs uniform circular motion, its velocity

• 不會改變。

  does not change.

• 不斷改變。

  is changing all the time.

• 沒有方向。

  does not have a direction.

• 總是指向同一方向。

  is always in the same direction.

一粒子繞一固定點作勻速圓周運動。以下有關該粒子的物理量，哪些會保持不變?

For a particle performing uniform circular motion about a fixed point, which of the following physical quantities of the particle remain unchanged?

• 速度

  velocity

• 加速度

  acceleration

• 動能

  kinetic energy

• 動量

  momentum

一男子在一圓柱形的「旋轉箱」內以恆速率轉動，他與牆壁保持緊貼。「旋轉箱」的地板是光滑的。以下哪個力提供該男子的向心力?

A man is rotating with constant speed inside a cylindrical ‘rotor’ and he remains pressed against the wall. The floor of the ‘rotor’ is smooth. Which of the following forces provides the centripetal force for the man?

• 該男子的重量

  the weight of the man

• 來自牆壁的摩擦力

  the frictional force from the wall

• 來自牆壁的法向反作用力

  the normal reaction from the wall

• 來自地板的承托力

  the supporting force from the floor

在一水平的圓形平台上，跟中心點O距離2r和r的地方分別固定着粒子P和Q，而平台如圖所示以勻速轉動。P與Q的角速率之比為

Particles P and O are fixed at distances 2r and r respectively from the centre O of a horizontal circular platform which is rotating uniformly as shown. The ratio of the angular speed of P to that of O is

• 1:1

• 2:1

• 4:1

• 1:2

在一水平的圓形平台上，跟中心點O距離2r和r的地方分別固定着粒子P和Q，而平台如圖所示以勻速轉動。P與Q的線速率之比為

Particles P and O are fixed at distances 2r and r respectively from the centre O of a horizontal circular platform which is rotating uniformly as shown. The ratio of the linear speed of P to that of O is

• 1:1

• 2:1

• 4:1

• 1:2

在一水平的圓形平台上，跟中心點O距離2r和r的地方分別固定着粒子P和Q，而平台如圖所示以勻速轉動。P與Q的加速度之比為

Particles P and O are fixed at distances 2r and r respectively from the centre O of a horizontal circular platform which is rotating uniformly as shown. The ratio of the acceleration of P to that of O is

• 1:1

• 2:1

• 4:1

• 1:2

在一水平的圓形平台上，跟中心點O距離2r和r的地方固定着兩粒相同的粒子P和Q，而平台如圖所示以勻速轉動。P與Q的動量之比為

Two identical particles P and O are fixed at distances 2r and r respectively from the centre O of a horizontal circular platform which is rotating uniformly as shown. The ratio of the momentum of P to that of O is

• 1:1

• 2:1

• 4:1

• 1:2

在一水平的圓形平台上，跟中心點O距離2r和r的地方固定着兩粒相同的粒子P和Q，而平台如圖所示以勻速轉動。P與Q的動能之比為

Two identical particles P and O are fixed at distances 2r and r respectively from the centre O of a horizontal circular platform which is rotating uniformly as shown. The ratio of the KE of P to that of O is

• 1:1

• 2:1

• 4:1

• 1:2

物體作勻速圓周運動時，它的向心力 F

When an object performs uniform circular motion, its centripetal force F

• $F=\frac{mv^2}{r}=mr\omega^2$

• $F=mrv^2=\frac{m\omega^2}{r}$

• $F=mrv^2=mr\omega^2$

• $F=\frac{mv^2}{r}=\frac{m\omega^2}{r}$

將一個質量為 1 kg 的茶壺放置於水平轉盤上，茶壺距離轉盤中心 30 cm，當轉盤旋轉時，茶壺保持在轉盤上的同一位置。指出什麼力茶壺提供向心力。

A teapot of mass 1 kg is put 30 cm from the centre of a horizontal turntable. When the turntable is rotating, the teapot remains at the same position on the turntable. Name the force that provides the centripetal force for the teapot.

• 張力 Tension

• 摩擦力 Friction

• 法向反作用力 Normal reaction

• 重量 Weight