You pull on a crate with a rope.  If the crate moves, the rope's pull on the crate must have been larger than the crate's pull on the rope, but if the crate does not move, both of these pulls must have been equal. true or false

Expert Answers

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The upward force on the rope is am where a is the acceleration of the rope and crate upwards and m is the mass of the crate (the mass of the rope is negligible).

The downward force on the rope is mg where g is the acceleration due to gravity.

The force T (tension) that the rope exerts equally on the crate and the mass moving the rope is then equal to the sum of the forces acting on it,

ie

T = m(a+g)

The force F that the crate exerts on the rope is equal to mg

If the crate isn't moving, a = 0 and so T = F

If the crate is moving upwwards then a > 0 and T > F

answer: true

Approved by eNotes Editorial Team

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