You are an employee of the city of Chicago. A city official declares that all cables holding traffic lights in the city should be exactly horizontal and asks you to direct the project. What should be your reply?

A. That's impossible, because according to Newton's Second Law, there must be an upward component of the tension in the cable that balances the weight of the traffic light, and therefore, the cable can never be exactly horizontal.

B. No problem. All we have to do is increase the horizontal tension in the cable.

C. No problem. All it takes is a pay raise.

D. That's impossible, because by Newton's Third Law, the cable pulls horizontally on the poles with a force of the same magnitude force as the force with which the poles pull on the cable. Therefore, if the horizontal component of the tension is too large, it will pull the poles inward toward the cables.

Question

Physics

Kaya Sheppard

22 June, 15:00

You are an employee of the city of Chicago. A city official declares that all cables holding traffic lights in the city should be exactly horizontal and asks you to direct the project. What should be your reply?

A. That's impossible, because according to Newton's Second Law, there must be an upward component of the tension in the cable that balances the weight of the traffic light, and therefore, the cable can never be exactly horizontal.

B. No problem. All we have to do is increase the horizontal tension in the cable.

C. No problem. All it takes is a pay raise.

D. That's impossible, because by Newton's Third Law, the cable pulls horizontally on the poles with a force of the same magnitude force as the force with which the poles pull on the cable. Therefore, if the horizontal component of the tension is too large, it will pull the poles inward toward the cables.

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Answers (1)

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Benson · Answer 1

If you have ever lived in Chicago, then the answer might very well be C.

Newton's Second law states F = ma. This problem has nothing to do with acceleration.

Newton's Third law is the familiar action/reaction law. If the poles are anchored well enough and have a flexural strength greater than the tension exerted on them by the wire; then D is just.

That leaves B. There's no problem all we have to do is to increase the horizontal tension in the cable.