Calculating Work on a Moving Crate with an Inclined Rope

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In summary, the question asks for the work done on a crate being pulled at a constant speed with a rope at an angle of 43.5 degrees. The tension in the rope is 115 N and the crate is moved 8.0 m. Using the equation W=Fd, the work done on the crate is calculated to be 115cos(43.5)8.0. However, since the total mechanical energy of the crate remains unchanged, the net work on the crate must be zero. Therefore, there is no need to factor in friction when calculating work in this scenario. The final answer should have the correct units to receive full marks.
  • #1
trikat
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Homework Statement


A 51-kg packing crate is pulled with a constant speed across a rough floor with a rope that is at an angle of 43.5 degrees above the horizontal. if the tension in the rope is 115 N, how much work is done on the crate to move it 8.0 m?

Homework Equations


Do we use frictional force when calculating work?

The Attempt at a Solution


W=Fd where F is the force only in the x direction. W=115cos(43.5)8.0[/B]
 
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  • #2
Welcome to PF;
Did you have a question?

The approach looks good to me - what you have done so far would get you 2 out of a possible 3 marks from me.
 
  • #3
Well, my specific question was if I have to factor in friction/when I have to factor in friction to work in general. Why 2 out of 3 marks? Because I didn't simplify my answer?
 
  • #4
You are right to wonder - the question asks for the work done on the crate, but does not tell you which force to consider.
Since the total mechanical energy of the crate remains unchanged, the net work on the crate must be zero.
(Well, the crate maybe got hotter.)

You may want to make sure the crate does, indeed, stay on the floor. I didn't check.
You have calculated the work done by the applied force - which is usually what questions written that way intend.

I would normally give one mark at this level for the correct units on the final answer.
 
  • #5
Oh! I always forget that constant velocity means that acceleration is zero, which means there's no force. No force means that there's no net work, if I'm understanding you correctly. Thanks for clearing that up!
 
  • #6
That's right - you just need to use your knowledge of how your teacher sets things up to work out if the question wants the work done by the applied force or the total change in mechanical energy.
 

1. What materials are typically used to make a packing crate?

Packing crates are typically made from wood, such as pine or cedar, due to its strength and durability. Some crates may also be made from plastic, metal, or cardboard depending on the specific use and transportation needs.

2. How do you determine the appropriate size for a packing crate?

The size of a packing crate is typically determined by the dimensions of the objects being packed. It is important to leave enough space for proper packaging materials and to ensure the crate can safely hold the weight of the contents. The dimensions can also be adjusted based on the mode of transportation and any size restrictions.

3. Are there any regulations or guidelines for packing crates?

Yes, there are regulations and guidelines for packing crates, especially for international shipments. These may include restrictions on the materials used, size and weight limits, and specific labeling requirements. It is important to research and follow these regulations to ensure safe and legal transportation of goods.

4. How do you ensure the safety and security of items in a packing crate?

There are several steps that can be taken to ensure the safety and security of items in a packing crate. This includes using sturdy and appropriate materials, properly packing and securing the items inside, and labeling the crate with any necessary warnings or handling instructions. It is also important to properly seal the crate to prevent any damage or tampering during transport.

5. Can packing crates be reused?

Yes, packing crates can be reused if they are still in good condition. This can help reduce waste and save money on purchasing new crates for each shipment. It is important to inspect the crate for any damage or wear and tear before reuse and make any necessary repairs.

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