A horizontal uniform bar of mass m and length L is hung horizontally on two vertical strings. String 1 is attached to the end of the bar and string 2 is attached a distance L/4 from the other end. A monkey of mass m/2 walks from one end of the bar to the other. Find the tension T1 in string 1 at the moment that the monkey is halfway between the ends of the bar.

**Please see attachment for complete question including hints and instructions

PSS 13.2: Walking the Plank

Learning Goal: To practice Problem-Solving Strategy 13.2 for problems

involving equilbrium of rigid bodies.

in string 1 at the moment that the monkey is halfway between the ends

of the bar.

MODEL:Â Â Model the object as a simple shape.

VISUALIZE:Â Â Draw a pictorial representation that shows all forces and

distances. List known information.

Pick any point you wish as a pivot point. The net torque about this

point is zero.

Determine the moment arms of all forces about this pivot point.

Determine the sign of each torque about this pivot point.

SOLVE:Â Â The mathematical representation is based on the fact that an

object in total equilibrium experiences neither a net force nor a net

torque. Thus,

.

.

Solve the three simultaneous equations.

ASSESS:Â Â Check that your answer is reasonable and answers the

question.

Model

We start by making simplifying assumptions appropriate for the

situation.

The bar should be modeled as

a particle moving with constant acceleration.

a flexible rod moving with constant acceleration.

a rigid rod moving with constant acceleration.

a particle in total equilibrium.

a flexible rod in total equilibrium.

a rigid rod in total equilibrium.

Visualize

Now draw a sketch, labeling all forces and distances. Use your sketch to

answer the following questions.

Which of the following diagrams correctly represents the forces acting

at the moment described in the problem introduction? (Note that the

forces are not necessarily drawn to scale.)

What is the distance between the monkey and string 2?

.

?

the center of mass of the bar

the point of attachment of string 1

the point of attachment of string 2

the end of the bar closest to string 2

Solve

Now use the information and the insights that you have accumulated to

construct the necessary mathematical expressions and to derive the

solution.

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Assess

When you work on a problem on your own, without the computer-provided

feedback, only you can assess whether your answer seems right. The

following questions will help you practice the skills necessary for such

an assessment.

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