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Inner and outer radii of a spool are r a...

Inner and outer radii of a spool are `r` and `R` respectively. A thread is wound over its inner surface and placed over a rough horizontal surface. Then:
.

A

Thread unwinds, spool rotates anticlockwise and friction acts leftwards

B

Thread winds, spool rotates clockwise and friction acts leftwards

C

Thread winds, spool moves to the right and friction act rightwards

D

Thread winds, spool moves to the right and friction does not come into existence

Text Solution

Verified by Experts

The correct Answer is:
B

For pure rolling point of contact must be the rest. `(a + R alpha = 0)` For that spool must rotate clock wise.
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Knowledge Check

  • Inner and outer radii of a spool are r And R respectively. A thread is wound over ita ineer surface and placed over a rough horizontal surface. Thread is pulled by a force F as shown in the figure. Then in case of pure rolling.

    A
    thread unwinds, spool rotates anticlockwise and friction leftwards
    B
    thread winds, spool rotates clockwise and friction leftwards
    C
    thread winds, spool moves to the right and friction acts rightwards
    D
    thread winds, spool moves to the right and friction does not come into existence

  • Inner and outer radii of a spool are r and R I , respectively. A thread is wound over its inner surface and spool is placed over a rough horizontal surface. Thread is pulled by a force F as shown in Fig. In case of pure rolling, which of the following statements are false?

    A
    Thread unwinds, spool rotates anticlockwise and friction acts leftwards.
    B
    Thread winds, spool rotates clockwise and friction acts leftwards.
    C
    Thread winds, spool moves to the right and friction acts rightwards.
    D
    Thread winds, spool moves to the right and friction does not come into existence.

  • A spool of mass m has moment of inertia I= 2mR^(2) about its axis of symmetry. The inner and outer radius of spool R and 2R respectively. Thread is wounded on the inner cylinder and its one end is pulled a force F acting at angle theta with horizontal. The surface is sufficiently rough and th.e spool never slides on the surface. For theta=0^(@) , the acceletation of spool is

    A
    `F/m`
    B
    `F/(2m)`
    C
    `F/(6m)`
    D
    `F/(3m)`

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