Rope with mass pulling a block

In summary: Then you can ask yourself the same question: why does the tension in the middle of the string exert a smaller force on the block than the tension on the ends of the string? Because the mass of the middle of the string is negligible compared to the masses at the ends of the string.
  • #1
JamesGold
39
0

Homework Statement



5OpuR.png


Homework Equations



f = ma

The Attempt at a Solution



I need help with all parts of this problem, but here are my comments on part a and c:

a) the block has its normal force vector pointing up and its weight vector pointing down. the tension of the rope is pulling it to the right. I'm very confused about the rope's free body diagram.

c) Why should the magnitude of the force that the rope exerts on the block be any different from the magnitude of the force pulling the rope to the right?
 
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  • #2
JamesGold said:

Homework Statement



5OpuR.png


Homework Equations



f = ma

The Attempt at a Solution



I need help with all parts of this problem, but here are my comments on part a and c:

a) the block has its normal force vector pointing up and its weight vector pointing down. the tension of the rope is pulling it to the right.
Yes , but the rope tension is variable. When drawing a free body diagram of the block alone, the tension force is the rope tension at the connection to the block.
I'm very confused about the rope's free body diagram.
which is not the same as the block's free body diagram. The rope has mass. Isolate the full length of rope. F - Tmin = m_r(a)
c) Why should the magnitude of the force that the rope exerts on the block be any different from the magnitude of the force pulling the rope to the right?
Because in this problem, the rope has mass . The rope tension is F only at the pulling end. It is smaller at the other end where it attaches to the block.
For starters, answer part b first, looking at the rope/block system.
 
Last edited:
  • #3
JamesGold said:

Homework Statement



5OpuR.png


Homework Equations



f = ma

The Attempt at a Solution



I need help with all parts of this problem, but here are my comments on part a and c:

a) the block has its normal force vector pointing up and its weight vector pointing down. the tension of the rope is pulling it to the right. I'm very confused about the rope's free body diagram.

c) Why should the magnitude of the force that the rope exerts on the block be any different from the magnitude of the force pulling the rope to the right?

You are probably more familiar with problems using a massless [light] string.

To get a feel for this situation, you might like to replace the heavy string, with a light one BUT with a mass added in the middle of the string. - pulling two masses tied together if you like.
 

1. How does the mass of the rope affect the pulling force on the block?

The mass of the rope does not directly affect the pulling force on the block. The force applied by the rope on the block is determined by the tension in the rope, which is dependent on the force applied to the rope and the angle at which the rope is pulling.

2. What is the relationship between the angle of the rope and the pulling force on the block?

The angle of the rope affects the pulling force on the block by changing the direction of the tension force. The greater the angle of the rope, the more the force is directed horizontally, resulting in a larger pulling force on the block.

3. How does the mass of the block affect the tension in the rope?

The mass of the block does not directly affect the tension in the rope. However, the weight of the block will contribute to the overall force that needs to be applied to overcome the weight of the block and move it.

4. Can the pulling force on the block be greater than the weight of the block?

Yes, the pulling force on the block can be greater than the weight of the block. In order to move the block, the pulling force needs to be greater than the weight of the block and any additional friction or resistance.

5. How does the coefficient of friction between the block and the surface it's on affect the pulling force?

The coefficient of friction between the block and the surface it's on affects the pulling force by increasing the resistance and making it more difficult to move the block. A higher coefficient of friction will require a greater pulling force to overcome the friction and move the block.

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