Anonymous asked in Science & MathematicsPhysics · 1 month ago

How does the tension of the cable compare to the weight of the beam?

A helicopter is used to lift a metal beam with an unknown mass of m with a cable. The helicopter is stationary, and the beam is pulled upwards by reeling in the cable. You notice the beam rising at a constant speed. During this time, the tension T in the cable compares to the weight mg of the beam as....

a) T>mg

b) T=mg

c) Cannot determine without mass of beam.

d) T<mg

1 Answer

  • 1 month ago

    The constant speed is part of the key.  The net force on the beam is zero.  This requires a force at the bottom of the cable of mg.  That is the tension in the cable AT THIS POINT. Higher up the cable the tension must support the lower part of that cable.  ie (m1+m) g

    Therefore none of the answers are adequate.  The tension in the cable is different at different points.  Unless the cable is massless.

    This was the problem in laying the transatlantic cable a century and a half ago.  The tension at the top could be so great that it snapped the cable even though the tension at the bottom was close to zero.

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