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International Baccalaureate · IB Diploma · Physics · HL Topik 4 4:04 Narasi bahasa Inggris · Subtitle bahasa Inggris + 中文 disematkan langsung
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A door is easier to open when pushed near its outer edge.
在门的外边缘附近推门更容易打开。
Force size alone does not determine the turning effect.
仅凭力的大小无法决定转动效果。
Torque depends on force and perpendicular distance from the axis.
力矩取决于力和到轴的垂直距离。
Moment of inertia describes resistance to angular acceleration and depends on mass distribution about a stated axis.
转动惯量描述了抵抗角加速度的能力，并取决于关于指定轴的质量分布。
Torque is the turning effect about an axis.
力矩是绕轴的转动效应。
Moment of inertia is the resistance to angular acceleration about a specified axis.
转动惯量是绕指定轴抵抗角加速度的能力。
For a rigid body about a fixed axis, net torque equals moment of inertia multiplied by angular acceleration.
对于绕固定轴转动的刚体，合外力矩等于转动惯量乘以角加速度。
Rotational kinetic energy depends on angular speed squared.
旋转动能取决于角速度的平方。
Angular momentum is conserved when net external torque is zero.
当合外力矩为零时，角动量守恒。
In the lab: Draw the pivot, force direction and perpendicular lever arm.
在实验室中，画出支点、力的方向和垂直力臂。
Do not use the sloping distance from pivot to force point unless it is perpendicular to the force.
除非从支点到作用点的斜线距离与力垂直，否则不要使用该斜线距离。
For experiments, keep rotating parts guarded and loads secure.
进行实验时，确保旋转部件有防护装置，且负载固定牢靠。
Known: a 10 N perpendicular force acts 0.30 m from an axis.
已知：一个 10 N 的垂直力作用在距离转轴 0.30 m 处。
Torque equals force times perpendicular distance, which is 10 times 0.30, equaling 3.0 N m.
力矩等于力乘以垂直距离，即 10 × 0.30 = 3.0 N·m。
If the moment of inertia is 0.60 kg square metres, angular acceleration equals torque divided by inertia, which is 3.0 divided by 0.60, equaling 5.0 radians per second squared.
若转动惯量为 0.60 kg·m²，则角加速度等于力矩除以转动惯量，即 3.0 / 0.60 = 5.0 rad/s²。
Your turn: A 12 N force acts perpendicularly 0.25 m from the pivot.
请作答。 一个12 N的力垂直作用在距离支点0.25 m处。
Find torque.
求力矩。
Pause the video and work it out.
请暂停视频，自己算一算。
Check: 12 newtons times 0.25 metres gives a torque of 3.0 newton metres.
核对：12 牛 × 0.25 米，力矩为 3.0 牛·米。
Torque has unit N m but is a turning effect, not an energy store.
力矩的单位是牛顿米，但它是转动效应，而非能量储存。
Moment of inertia changes if the same mass moves farther from the axis.
若相同质量远离转轴移动，转动惯量会发生变化。
Not true: Moment of inertia depends only on total mass, never its distribution.
这种说法不正确。 转动惯量不仅取决于总质量，还取决于质量的分布情况。
Moment of inertia depends on how mass is distributed relative to the axis: the same total mass farther from the axis gives a larger moment of inertia.
转动惯量取决于质量相对于转轴的分布方式。 在总质量相同的情况下，质量离转轴越远，转动惯量越大。
That is why a skater spinning with arms extended slows when the arms are pulled in.
这就是为什么花样滑冰运动员在伸展手臂旋转时，当把双臂收回身体时转速会加快的原因。
Torque depends on force and perpendicular distance from the axis.
力矩取决于力的大小以及到转轴的垂直距离。
For a rigid body about a fixed axis, net torque equals moment of inertia multiplied by angular acceleration.
对于绕固定轴转动的刚体，合力矩等于转动惯量乘以角加速度。
Watch for: torque has unit N m but is a turning effect, not an energy store.
请注意：力矩的单位是牛顿米，但它表示的是转动效应，而非能量储存。
A twenty newton force acts perpendicularly, zero point four zero metres from the pivot.
一个20 N的力垂直作用在距离支点0.40 m处。
Find the torque.
求力矩。
Moment of inertia depends on how mass is distributed.
转动惯量取决于质量的分布情况。
The result is a torque of 8 newton metres.
结果是力矩为8牛米。
Torque depends on the force and on its perpendicular distance from the axis.
力矩取决于力的大小以及力到转轴的垂直距离。
Ten newtons at 0.30 metres gives 3.0 newton metres.
10牛的力作用在0.30米处，力矩为3.0牛米。
A 12 N force acts 0.50 m from a pivot at 30° to the lever.
一个12牛顿的力作用在距离支点0.50米处，与杠杆成30度角。
Find torque and compare a perpendicular force at the same radius.
求力矩，并与同一半径处的垂直力进行比较。
The torque is r F sine 30 degrees, which is 3.0 newton metres; applied perpendicular, the torque is 6.0 newton metres.
力矩等于r乘以F乘以sin30°，即3.0 N·m。 垂直力矩为6.0 N·m。
Use the perpendicular moment arm and state the rotation sign convention.
请使用垂直力臂并说明旋转符号约定。
Pause and check yourself. Explain each point on screen in your own words, then change one number in the last example and say which assumption must still hold.
暂停一下，自我检查：用自己的话解释屏幕上的每个要点，再改动最后一个例子中的一个数字，说明哪个假设仍然必须成立。