Master the FBD Technique: Superhero & Sidekick Hanging on a Rope

[cmkc109]

Homework Statement

A superhero and his sidekick are hanging motionless from a rope.
The superhero’s mass is 90.0kg, while the sidekick’s mass is

Homework Equations

The Attempt at a Solution

i tried drawing it out, but not sure
so I divided the rope into two points, one on the superhero and the other on the sidekick
and I'm not sure where tension is acting..

I would say Tension that the superhero has on the rope is acting upwards..I actually dunno..VERY VERY CONFUSING

 

[ehild]

The two pieces of the rope have different tensions. Tension acts at both ends, with opposite signs. The piece below acts downward to superhero, and the piece above him acts upward.

ehild

 

[cmkc109]

does the rope exert the tension or the superhero exert the tension?
when i draw the FBD, where does the point start? with reference to the centre of mass of each person or the rope? thanks

 

[ehild]

does the rope exert the tension or the superhero exert the tension?
when i draw the FBD, where does the point start? with reference to the centre of mass of each person or the rope? thanks

Do you know Newton's third Law? The rope acts at the man with its tension. The man exerts force on the rope.

You can consider both men as point masses (a bit big points :tongue2:), all mass compressed in the CM. When drawing the forces acting on a man, you can draw the arrows starting at the CM, but it is also correct and more clear if you draw one arrow at the foot and the other at the hands.ehild

 

[Nickie]

!!!

I understand your confusion and I am here to help. Let's break down the problem using the Free Body Diagram (FBD) technique.

First, let's identify the forces acting on the system. We have the weight of the superhero and the sidekick, which are both acting downwards due to gravity. We also have the tension force from the rope, which is acting upwards to support the weight of the two individuals.

Next, we need to determine the direction of the tension force. Since the superhero and sidekick are hanging motionless, we can assume that the tension force is equal to the weight of the two individuals combined. Therefore, the tension force is acting upwards from the point where the rope is attached to the ceiling.

Now, let's draw our FBD. We will have two points, one for the superhero and one for the sidekick, with arrows representing the forces acting on each point. The superhero's FBD will have an arrow pointing downwards to represent his weight of 90.0kg, and an arrow pointing upwards to represent the tension force. The sidekick's FBD will have an arrow pointing downwards to represent his weight, and an arrow pointing upwards to represent the tension force.

To solve for the tension force, we can use Newton's second law, which states that the net force on an object is equal to its mass multiplied by its acceleration. Since the superhero and sidekick are hanging motionless, their acceleration is zero. Therefore, the net force on each individual must also be zero. This means that the tension force must be equal to their combined weight.

In summary, the key to mastering the FBD technique in this problem is to identify the forces acting on the system, determine the direction of the tension force, and use Newton's second law to solve for the tension force. I hope this helps you in approaching similar problems in the future. Keep practicing and you will master the FBD technique in no time!