Question

A farmer tosses a rope over a beam at the top of a barn. He ties one end of the rope to a bale of hay. He then raises the bale up to the barn loft by pulling down on the loose end of the rope. Why does the input force have to be greater than the force needed to lift the bale? a. Friction increases the effect of the input force. b. Friction eliminates the work input. c. Friction reduces the work input.

Answer 1

Answer:

Option A, Friction increases the effect of the input force.

Explanation:

The beam tied to the top of barn is not a friction less  lever as are the pulleys.

Due to this some frictional force will arise at the point of contact of rope and the beam.

Now in order to lift the bale of hay , a person pulling the rope has to apply force greater than the weight of hay in order to overcome the frictional forces arising due to beam.

Therefore the   input force have to be greater than the force needed to lift the bale

Hence, option A is correct

Answer 2

Answer:

The correct answer is option c, that is, friction reduces the work input.

Explanation:

In the given case, the farmer tosses a rope over a beam, that is, at the top of the barn, he then knots one terminal of the rope to a bale of hay and then elevates the bale up to the barn loft by pulling down on the loose terminal of the rope. At the time of this whole procedure, it is known that the force of friction present on the barn will prevent the movement of rope over it because of which the total force imparted on the rope gets diminished. Thus, here the work done on the rope will get reduced because of the effect of the friction, which is in contrast to the force applied.