# Don't Rock the Block

PSS 5.1: Don't Rock the Block

Learning Goal: To practice Problem-Solving Strategy 5.1 for equilibrium problems.

A pair of students are lifting a heavy trunk on move-in day . Using two ropes tied to a small ring at the center of the top of the trunk, they pull the trunk straight up at a constant velocity . Each rope makes an angle with respect to the vertical. The magnitude of the weight of the trunk is .

Find the tension in each rope.

MODEL: Make simplifying assumptions.

VISUALIZE:

â€¢ Physical representationâ€”Identify all forces acting on the object and show them on a free-body diagram.

â€¢ Pictorial representationâ€”The free-body diagram is usually sufficient as a picture for equilibrium problems, but you still must translate words into symbols and identify what the problem is trying to find.

It is acceptable practice to go back and forth between these two steps as you visualize the situation.

SOLVE: The mathematical representation is based on Newton's 1st law:

The vector sum of the forces is found directly from the free-body diagram.

A. Which of the following statements are correct?

A. The x component of the weight of the trunk is zero.

B. The y component of the weight of the trunk is zero.

C. The x components of the forces of tension in the ropes have the same magnitude and sign.

D. The x components of the forces of tension in the ropes have the same magnitude and opposite sign.

E. The y components of the forces of tension in the ropes have the same magnitude and sign.

F. The y components of the forces of tension in the ropes have the same magnitude and opposite sign.

G. The x component of the acceleration of the trunk is zero.

H. The y component of the acceleration trunk is zero.

I. The angle between the ropes is .

J. The angle between the ropes is .

https://brainmass.com/physics/acceleration/dont-rock-block-29064

#### Solution Preview

PSS 5.1: Don't Rock the Block

Learning Goal: To practice Problem-Solving Strategy 5.1 for equilibrium problems.

A pair of students are lifting a heavy trunk on move-in day . Using two ropes tied to a small ring at the center of the top of the trunk, they pull the trunk straight up at a constant velocity . Each rope makes an angle with respect to the vertical. The magnitude of the weight of the trunk is .

Find the tension in each rope.

MODEL: Make simplifying ...

#### Solution Summary

The solution provides explanations for the physics behind the movement of a trunk by two people holding it with a rope on either side. Calculations and diagrams are provided.