Calculate Upper Scale Reading for Suspended 50kg Crate Using Spring Scales

  • Thread starter mikefitz
  • Start date
  • Tags
    Pulleys
In summary, the problem involves a 50-kg crate suspended between the floor and the ceiling using two spring scales. The lower scale reads 121 N and the upper scale is being questioned. The upper scale should read 369 N, as the total weight of the crate is 490 N (converted from 50 kg). The lower scale is not supporting the crate, but pulling down on it. The notes given by the teacher do not match the problem and are for a separate problem involving an Atwood's machine.
  • #1
mikefitz
155
0
A 50-kg crate is suspended between the floor and the ceiling using two spring scales, one attached to the ceiling and one to the floor. If the lower scale reads 121 N, what is the reading of the upper scale? Ignore the weight of the scales.

So, I convert 50kg to N and get 490
Then I subtract 121 from 490 and get 369 N

Why isn't the reading on the ceiling 369; wouldn't that make sense? Thanks
 
Physics news on Phys.org
  • #2
mikefitz said:
A 50-kg crate is suspended between the floor and the ceiling using two spring scales, one attached to the ceiling and one to the floor. If the lower scale reads 121 N, what is the reading of the upper scale? Ignore the weight of the scales.

So, I convert 50kg to N and get 490
Then I subtract 121 from 490 and get 369 N

Why isn't the reading on the ceiling 369; wouldn't that make sense? Thanks
Why did you subtract 121N? The lower scale is not supporting the crate, it's pulling down on it.
 
  • #3
I thought the two readings would have to equal the total mass of the crate? My understanding of pulleys is really lacking, and these notes given to me from my teacher make little sense (he is not the best instructor and has failed to give me a good explanation for them)

Untitled-11.png
 
  • #4
Those notes don't match the problem you describe. Where the heck did the pulleys come from? According to the question in the OP, there are two spring scales, one aboved and one below. Take away the word "scale" and you have two springs. ONe pulls up, one pulls down. The one above will have to pull up with the force equal to the weight of the crate plus the amount by which the lower spring pulls down.

The notes are for "Atwood's" machine, that's a different problem.
 

FAQ: Calculate Upper Scale Reading for Suspended 50kg Crate Using Spring Scales

1. How do crates and pulleys work?

Crates and pulleys work together to lift heavy objects by using a system of ropes, cables, and one or more wheels. The ropes are threaded through the pulleys, which are attached to each other and to the crate. As one end of the rope is pulled, the pulleys rotate and lift the crate off the ground.

2. What are the benefits of using crates and pulleys?

The main benefit of using crates and pulleys is that they make it easier to lift and move heavy objects. By using multiple pulleys, the weight of the object is distributed across the ropes, making it possible for a single person to lift much more than they could on their own. This also reduces the risk of injury from lifting heavy objects.

3. What is the difference between a fixed pulley and a movable pulley?

A fixed pulley is attached to a stationary object, while a movable pulley is attached to the object being lifted. With a fixed pulley, the direction of the force needed to lift the object is changed, but the amount of force required remains the same. A movable pulley reduces the amount of force needed to lift the object, but the direction of the force remains the same.

4. How do you calculate the mechanical advantage of a crate and pulley system?

The mechanical advantage of a crate and pulley system can be calculated by dividing the weight of the object being lifted by the force applied to the rope. For example, if an object weighs 200 pounds and a force of 50 pounds is applied to the rope, the mechanical advantage is 4 (200/50). This means that the system is 4 times more efficient than lifting the object without the pulleys.

5. Can crates and pulleys be used to lift objects of any weight?

While crates and pulleys can greatly increase the amount of weight that can be lifted, there are limits to their capabilities. The strength of the materials used and the friction in the pulley system can affect the maximum weight that can be lifted. Additionally, the more pulleys that are used, the more efficient the system becomes, but it also increases the complexity and potential for failure.

Similar threads

How Does a Pulley System Affect Scale Readings?
Replies
8
Views
520
Absolute motion analysis of pulley-spring system
Replies
10
Views
557
Determining mass of a weight on a three spring scale setup
Replies
14
Views
3K
Two spring scales holding a hanging mass, what're the readings on both scales?
Replies
4
Views
15K
Weighing with A 400 N Scale and 80 N Spring Dynamometer
Replies
1
Views
8K
What is the acceleration of the upper crate when the top crate begins to slide?
Replies
10
Views
4K
Scale Hanging From Ceiling of Elevator Question
Replies
4
Views
7K
Forces acting on a box-pulley system in an elevator?
Replies
33
Views
7K
Determining scale readings given different densities
Replies
2
Views
1K
How Does a Spring Scale Measure the Total Force in a Balanced Meter Ruler Setup?
Replies
5
Views
5K

Hot Threads

Recent Insights

Back
Top