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Chapter 11: Problem 11

When you turn on a high-speed power tool such as a router, the tool tends to twist in your hands. Why?

Short Answer

Expert verified
The high-speed power tool tends to twist in your hands due to the conservation of angular momentum. When the tool is turned on, the motor inside starts spinning quickly in one direction, but since the overall angular momentum must stay zero (it was zero when the tool was stationary), the tool itself must start spinning in the opposite direction causing the twisting effect.

Step by step solution

01

Understand the law of conservation of angular momentum

According to the law of conservation of angular momentum, if a system is isolated (meaning no external torques are acting on it), the total angular momentum of the system remains constant. At rest, the system (power tool) has zero angular momentum.
02

Application of the law of conservation on a high-speed power tool

When the power tool is turned on, the motor inside starts spinning at a high speed, therefore gaining angular momentum. To keep total angular momentum constant (zero in this case), the tool itself (which you hold in your hands) has to gain an equal amount of angular momentum but in the opposite direction, as the system (tool + motor) should remain isolated.
03

Result of the conservation law application

The result of the conservation law mentioned in Step 2 is the tool twisting in your hands when it's turned on. From your point of view, the tool is trying to move in the opposite direction to the motor's spin inside, which results in a noticeable twist in your hands.

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