What is the Efficiency of the system?

  • Thread starter Thread starter kathy
  • Start date Start date
  • Tags Tags
    Efficiency System
AI Thread Summary
The discussion centers on calculating the efficiency of a hand crank system used to lift a 12.0 kg bucket of water 8.5 m with a force of 40.0 N over a distance of 15.0 m. The actual work done is calculated as 600 J, while the useful work done is determined to be 1000 J. This results in an efficiency calculation of 166%, which raises concerns since efficiency cannot exceed 100%. The discrepancy suggests there may be an error in the problem statement or assumptions made in the calculations. The discussion highlights the importance of verifying inputs and understanding the principles of work and efficiency in mechanical systems.
kathy
Messages
5
Reaction score
0
Question:

An hand crank is used to life a bucket of water from a well. The bucket and water have a combined mass of 12.0 kg and must be raised 8.5 m. The force used to lift this load is 40.0 N and must be applied over a total circular distance of 15.0 m. What is the efficiency of the system?

Related Equations:
W = (Force) (displacement)
W useful = (mass) (gravity) (height)
% Efficiency = useful work done / actual work done x 100%

Attempt at a Solution:

F = 40.0N
m = 12.0kg
h = 8.5m
g= 9.8N/kg
d= 15.0m
w= ?
w= (F)(d)
w= (40.0N) (15.0m)
w= 600J
w useful = ?
% Efficiency = ?
W useful = m g h
W useful = (12.0kg) (9.8N/kg) (8.5m)
W useful = 999.6J
w useful = 1000J
% Efficiency = useful work done / actual work done x 100%
% Efficiency = 1000J/600J x 100%
% Efficiency = 166%


The reason why I'm not sure I got the correct answer is because the efficiency of the system is over 100% instead of under...
?_?
 
Physics news on Phys.org
Looks like something wrong with the problem statement.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Thermodynamic Cycle -- Work done as a function of Heat absorbed
Replies
3
Views
2K
Efficiency of Ramp: Solving Box Push Up Problem
Replies
3
Views
3K
Energy Transformation Efficiency Problem
Replies
2
Views
1K
What is the meaning of work done for non-uniform circular motion?
Replies
11
Views
2K
Effeciency and Current Relationship
Replies
7
Views
2K
How Much Water Can a 1KW Carnot Engine Freeze in 5 Minutes?
Replies
3
Views
1K
What are the thermodynamic properties and efficiency of a steam plant?
Replies
9
Views
2K
Clausius-Clapeyron equation and absorbed heat
Replies
3
Views
2K
Efficiency of Objects Pushed Up a Ramp
Replies
5
Views
2K
Heat Exchange and Efficiency in a Fridge
Replies
10
Views
2K

Hot Threads

Recent Insights

Back
Top