Question

A phonograph record on turn table rotates 30 rpm . the linear speed of a point on the record at the needle at the beginning of the recording when it is at a distance of 14m from the centre is

1. 22cm/sec
2.44cm/sec
3.48cm/sec
4.52cm/sec

Answer 1

The distance should be 14 cm. check once

Answer 2

The linear speed of a point on the record at the needle at the beginning of the recording is 44 cm/s.

Explanation:

Given that,

Angular speed of the phonograph is 30 revolutions/minute

30 revolutions/minute = 3.14 rad/s

Distance from the center, r = 14 cm

To find,

The linear speed of a point on the record at the needle at the beginning of the recording is given by :

$v=r\omega$

$v=14\ cm\times 3.14\ rad/s$

v = 43.96 cm/s

or

v = 44 cm/s

So, the linear speed of a point on the record at the needle at the beginning of the recording is 44 cm/s.

Learn more :

Angular speed

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