Space Time & Motion A.2 Forces & Momentum (id: 5f9e54898)

本题目来源于试卷: Space Time & Motion A.2 Forces & Momentum，类别为 IB物理学

[单选题]
A CD stores data on its surface on a number of concentric circular tracks of different radii. The radius of the first track is 24 mm and that of the last track is 60 mm as shown in the diagram.

The data from the CD is read by rotating the disk under a laser system where the tangential speed is always 1.5 ${ms^{-1}}$for the track being read.

Which of the following is correct about the angular speed of the first track ω1 and the angular speed of the last track ω2?

A. 60${rad s^-1}$ ; same as ${\omega_1}$
B. 60${rad s^-1}$; less than ${\omega_1}$
C. 25${rad s^-1}$; same as ${\omega_1}$
D. 25${rad s^-1}$ ;greater than ${\omega_1}$


参考答案:  B


本题详细解析:

$\underline{\text{Explanation}}$:

Since the tangential speed is constant for all tracks, then the angular speed is different for each track.

The angular speed of the first track:

$$ ${\omega }_1={\displaystyle \frac{v}{r_1}}$

$$ ${\omega }_1={\displaystyle \frac{1.5}{25\times {10}^{-3}}}$

$$ $=60rad{s}^{-1}$

The angular speed of the last track will be less than that of the first track since the angular speed is inversely proportional to the radius of rotation.

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