Tension in ropes connecting blocks

In summary, the conversation discusses a figure with two 1.0 kg blocks connected by a rope, with a second rope hanging beneath the lower block. Both ropes have a mass of 250 g and the entire assembly is accelerated upward at 3.0 m/s^2. The force pulling the system is found to be 32.0N, but there is confusion about finding the tension at the top end of rope 1. The equations used to find the tension are discussed, but a mistake is made due to not accounting for the mass of the ropes. Instructions for how to properly solve the problem are given.
  • #1
sevens
8
0
The figure shows two 1.0 kg blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at
3.0 m/s^2
i found the force that pulls the system to be 32.0N
However the followup question states:
What is the tension at the top end of rope 1?

for a I have
[tex]
\sum{}\ = F - T = ma
[/tex]

and for b I have

[tex]
\sum{}\ = T - W = ma
[/tex]

since i knew my a was 3.0 m/s^2 i made the equations equal to each other, to find my tention.
[tex]
(T - W)m = (F-T)m
[/tex]

I arived at the answer 25.1N which is wrong. i think it may have to do with the fact that the ropes have a mass I thought tension through out a rope was uniform no matter where on the string you are. :grumpy:
 

Attachments

  • knight_Figure_08_26.jpg
    knight_Figure_08_26.jpg
    3.6 KB · Views: 1,023
Physics news on Phys.org
  • #2
sevens said:
The figure shows two 1.0 kg blocks connected by a rope. A second rope hangs beneath the lower block. Both ropes have a mass of 250 g. The entire assembly is accelerated upward at
3.0 m/s^2
i found the force that pulls the system to be 32.0N
However the followup question states:
What is the tension at the top end of rope 1?

for a I have
[tex]
\sum{}\ = F - T = ma
[/tex]

and for b I have

[tex]
\sum{}\ = T - W = ma
[/tex]

since i knew my a was 3.0 m/s^2 i made the equations equal to each other, to find my tention.
[tex]
(T - W)m = (F-T)m
[/tex]

I arived at the answer 25.1N which is wrong. i think it may have to do with the fact that the ropes have a mass I thought tension through out a rope was uniform no matter where on the string you are. :grumpy:

ok you do it the same way you did the first part, except this time you only count the mass until the end of the first rope. i did this problem a couple of weeks ago. you are doing it on online homework aren't you?
 
  • #3


Your approach to finding the tension in the ropes is correct, but there are a few things that may have led to your incorrect answer.

Firstly, when setting up your equations, make sure you are considering the forces acting on each block separately. For the top block, the equation would be: \sum F = T - W = ma, where T is the tension at the top end of rope 1, W is the weight of the top block, m is the mass of the top block, and a is the acceleration of the system (3.0 m/s^2). For the bottom block, the equation would be: \sum F = F - T = ma, where F is the force pulling the system (32.0 N), T is the tension at the bottom end of rope 1, and m is the mass of the bottom block.

Secondly, make sure you are using the correct value for the weight of the blocks. In this case, the weight of each block would be 1.0 kg multiplied by the acceleration due to gravity (9.8 m/s^2), which gives a weight of 9.8 N for each block.

Lastly, make sure you are taking into account the mass of the ropes when calculating the tension. In this case, the tension at the top end of rope 1 would be: T = ma + W + m(rope)g = (1.0 kg)(3.0 m/s^2) + (9.8 N) + (0.250 kg)(9.8 m/s^2) = 12.9 N + 9.8 N + 2.45 N = 25.15 N.

Overall, it is important to carefully consider all the forces acting on each block and to account for the mass of the ropes when calculating the tension.
 

1. What is tension in ropes connecting blocks?

Tension is the pulling force exerted on a rope when it is stretched between two objects. In the context of connecting blocks, tension is the force that keeps the blocks in place and prevents them from moving apart.

2. How is tension calculated in ropes connecting blocks?

Tension is calculated using Newton's Second Law of Motion, which states that force equals mass times acceleration (F=ma). In the case of ropes connecting blocks, the force of tension is equal to the weight of the blocks multiplied by the acceleration due to gravity.

3. What factors affect tension in ropes connecting blocks?

The tension in ropes connecting blocks is affected by the weight of the blocks, the length and material of the rope, and the angle at which the rope is pulling on the blocks. The greater the weight and the steeper the angle, the higher the tension will be.

4. How does tension change when one block is removed?

If one block is removed from a system of connected blocks, the tension in the remaining rope will decrease. This is because there is now less weight pulling on the rope, resulting in a lower overall tension force.

5. Can tension in ropes connecting blocks ever be greater than the weight of the blocks?

Yes, it is possible for the tension in ropes connecting blocks to be greater than the weight of the blocks. This can happen if the angle of the rope is steep enough, or if external forces such as wind or friction are acting on the blocks. However, in a stable system, the tension will always be equal to or less than the weight of the blocks.

Similar threads

  • Introductory Physics Homework Help
2
Replies
38
Views
975
  • Introductory Physics Homework Help
Replies
23
Views
1K
  • Introductory Physics Homework Help
Replies
10
Views
1K
  • Introductory Physics Homework Help
Replies
25
Views
3K
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
11
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
415
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
14
Views
2K
  • Introductory Physics Homework Help
Replies
13
Views
2K
Back
Top