Jerry's great grandmother's vitrola plays records at 78 roatations per minute (rpm). Describe what will happen if Jerry starts the vitrola on a friction free table. Justify your answer.
Jerry's great grandmother's vitrola plays records at 78 roatations per minute (rpm). Describe what will happen if Jerry starts the vitrola on a friction free table. Justify your answer.
The phonograph has a motor that makes the record kept on it rotate with respect to the phonograph’s body. The motor’s stator is fixed to the phonograph’s body and its rotor is attached to the record.
As per Newton’s third law, the motor applies an equal but opposite reaction to move the phonograph’s body but normally, the phonograph is steady on a surface. The friction offered by the surface under the phonograph keeps the phonograph’s body stationary.
In the absence of friction, the phonograph itself is not able to resist its own rotation. The reaction that the motor applies to the phonograph’s body is no longer countered by friction.
Hence, the phonograph will start rotating in the record’s opposite direction with a small angular speed, since a phonograph is usually much heavier than a record.
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