Don't Understand Tension in this Instance

  • Context: Undergrad 
  • Thread starter Thread starter Lexielai
  • Start date Start date
  • Tags Tags
    Tension
Click For Summary
SUMMARY

The discussion revolves around the physics of tension in a rope when a 72.0 kg man exerts a downward force of 358 N to hoist himself into a tree. The key conclusion is that the tension created in the rope, which equals the force exerted, results in a net upward force that exceeds the man's weight of 705.6 N, allowing for upward acceleration. The tension acts on both the man's body and his hands, leading to confusion about the sensation of force during the action. The explanation clarifies that even if the hands lower, an upward force is still transmitted through the arms to the torso.

PREREQUISITES
  • Understanding of Newton's Second Law of Motion
  • Basic knowledge of tension in ropes
  • Familiarity with free body diagrams
  • Concept of weight as W = mg
NEXT STEPS
  • Study free body diagrams to visualize forces in tension scenarios
  • Explore Newton's Second Law applications in different contexts
  • Research the mechanics of pulleys and their effect on tension
  • Investigate real-life applications of tension in climbing and lifting
USEFUL FOR

Physics students, educators, and anyone interested in understanding the mechanics of tension and forces in physical activities such as climbing or lifting.

Lexielai
Messages
3
Reaction score
0
Hello everyone!

I was doing a homework problem tonight, and a concept came up that I didn't quite understand. Don't worry, this is not a question asking for homework help -- I've already done the research and figured out how to solve for the solution. What I don't understand is why it's true.

For the sake of simplicity, I will be copying the homework problem here to clarify the circumstances.

To hoist himself into a tree, a 72.0 kg man ties one end of a nylon rope around his waist and throws the other end over a branch of the tree. He then pulls downward on the free end of the role with a force of 358 N. Neglect any friction between the rope and the branch, and determine the man's upward acceleration.

I've already researched a few other sources, so I know how the answer is derived, but I don't understand why it's true. In this instance, the man's exertion of 358 N creates a tension of 358. His weight, W = mg, is 705.6 N in this instance. Because tension acts on both ends of the rope, apparently, he rises because the tension is doubled, which would exceed 705.6 N and allow him to accelerate upwards.

According to the sources I've looked into, one end of the tension acts on his body, while the other acts on his hands. However, I have a hard time imagining a pulling force on his hands. When this action is done in real life, I don't feel as if my hands are being pulled upwards. Rather, my hands stay in the same location on the rope, and are possibly even lowered from their previous position while my body rises.

I suppose because the hands are a "part of the body" then the pulling force would transfer over to the body, but in that instance there would still be a pulling force on the hands. How does this force manifest? A picture/diagram would probably be very helpful in explaining this! ;)

Thanks in advance!
 
Physics news on Phys.org
Lexielai said:
When this action is done in real life, I don't feel as if my hands are being pulled upwards. Rather, my hands stay in the same location on the rope, and are possibly even lowered from their previous position while my body rises.
If you are pulling down on the rope, the rope must be pulling you up. Just because your hands lower, doesn't mean that an upward force isn't being exerted on your body. (The force is transmitted through your hand and arm to your torso.)
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 20 ·
Replies
20
Views
2K
  • · Replies 34 ·
2
Replies
34
Views
5K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 19 ·
Replies
19
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 14 ·
Replies
14
Views
1K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 40 ·
2
Replies
40
Views
4K