A telephone lineman is told to stretch the wire between two poles so the poles exert an 800N force on the wire. As the lineman does not have a scale to measure forces, he decides to measure the speed of a pulse created in the wire when he hits it with a wrench. The pulse travels 60m from one pole to the other and back again in 2.6s. The 60m wire has a mass of 15kg.

Should the wire be tightened or loosened?

A. Loosened

B. Tightened

Question

Physics

Fabian Mccormick

12 February, 22:52

A telephone lineman is told to stretch the wire between two poles so the poles exert an 800N force on the wire. As the lineman does not have a scale to measure forces, he decides to measure the speed of a pulse created in the wire when he hits it with a wrench. The pulse travels 60m from one pole to the other and back again in 2.6s. The 60m wire has a mass of 15kg.

Should the wire be tightened or loosened?

A. Loosened

B. Tightened

+3

Answers (2)

Know the Answer?

Emery Valdez · Answer 1

The answer is B, it should be tightened

Explanation:

To answer this question, we start by breaking down the parameters:

So we have,

Force = 800 Newton

Distance of pulse traveled = 60 meters

Time to travel for 60 meters = 2.6 seconds.

Mass of wire = 15kg

After careful study of the narrative of the question and the parameters, we can say that the relationship between the force exerted on the rope, distance of pulse traveled and the time to travel the distance is equivalent to:

v = √ F / μ

where μ = m / L

where m = mass and L = length of the wire

therefore,

if we assume that the weight of the wire is uniformly distributed across the length of the wire and in a case where we have been given the mass of the wire to be 15kg and the length to be 60m.

Applying the above equation, we have:

15kg / 60m = 0.25 kg / m

Again, if we consider calculating the velocity or speed of the pulse.

We will have:

Speed = distance / time

Speed = 2 x 60m / 2.6 sec

= 46.15 m / s

If we now decide to make Force the subject of the formula,

we will have:

F = μv²

if we now insert the values, we will have:

F = 532,5 Newton.

Now, we can conclude that the wire should be tightened since the initial force in the wire is less than the required force.

Jesse Faulkner · Answer 2

Answer: f = 532.46 N

Explanation:

V = √ (f / u) is the formula that describe the relationship between the speed of a pulse moving on a rope, and the force being exerted on the rope.

u = m / L, such that

u = 15 / 60

u = 0.25 kg/m

We calculate the speed of the pulse

v = distance / time

v = (2 * 60) / 2.6

v = 46.15 m/s

v = √ (f / u)

F = uv²,

F = 0.25 * 46.15 * 46.15

F = 532.56 N

The rope should be tightened because the force in the wire is less than the required force.