Help please, power (piano pulled up by workers through pulley)

  • Thread starter Thread starter xregina12
  • Start date Start date
  • Tags Tags
    Power Pulley
Click For Summary
SUMMARY

A 3.50 kN piano is lifted 25 m by three workers using a pulley system with 75% efficiency. Each worker contributes 165 W of power, totaling 495 W. However, due to the pulley’s efficiency, only 371.25 W (75% of 495 W) is effectively used to lift the piano. The time required to lift the piano can be calculated using the formula time = work done / effective power, leading to a total lift time of approximately 67.5 seconds.

PREREQUISITES
  • Understanding of basic physics concepts such as force, work, and power
  • Familiarity with the equations of motion and energy transfer
  • Knowledge of efficiency calculations in mechanical systems
  • Ability to manipulate units of measurement (Watts, Joules, Newtons)
NEXT STEPS
  • Calculate the work done in lifting the piano using the formula Work = Force x Distance
  • Explore the concept of mechanical efficiency and its impact on power transmission
  • Learn about the principles of pulleys and their applications in lifting systems
  • Investigate the relationship between power, work, and time in physics
USEFUL FOR

Physics students, engineers, and anyone interested in understanding mechanical systems and power calculations in lifting scenarios.

xregina12
Messages
26
Reaction score
0
A 3.50 kN piano is lifted by 3 workers at constant speed to an apartment 25 m above ground. Each worker is able to deliver 165 W of power and the pulley is 75% efficient (25% lost due to friction on pulley). Neglecting mass of pulley, what is the time required to lift the piano from the street to the apartment.
I know that F=T-mg=ma=0
T=3500N
Work=3*165=495W=F/t
But I'm not really sure how to sort this problem out and incorporate the 75% efficiency of the pulley and the height above ground. Please help me.
 
Physics news on Phys.org
xregina12 said:
Work=3*165=495W=F/t

Not quite. You are equating work (units: Joules) with power (units: Watts) here, but they are not the same. And neither of those would equal force/time.

At any rate, 495W is the power exerted by the 3 people. So how much of that power gets transmitted to the piano? (hint: it is not 100% of the power)
 

Similar threads

What is the power input of a motor pulling up an elevator?
  • · Replies 3 ·
Replies
3
Views
3K
How Much Power Does an Escalator Need to Operate Fully Laden?
  • · Replies 8 ·
Replies
8
Views
8K
Power/Work problem with some Newton's Second Law
  • · Replies 2 ·
Replies
2
Views
3K
Pulley with 2 Blocks on an Inclined Plane. Help please
  • · Replies 3 ·
Replies
3
Views
13K
What Is the Average Power Delivered in Lifting a Box with Constant Acceleration?
  • · Replies 2 ·
Replies
2
Views
7K
What is the Power Delivered by the Person Pulling the Rope?
  • · Replies 5 ·
Replies
5
Views
7K
Calculate Time to Lift Piano: 132kg Piano, 7.3m High, 470W Power
  • · Replies 3 ·
Replies
3
Views
2K
Power Needed for 200kg Glider to Reach 25m/s in 75m
  • · Replies 2 ·
Replies
2
Views
2K
How much time does it take to lift the piano?
  • · Replies 2 ·
Replies
2
Views
3K
Power Needed to Pull Skier Up Slope
  • · Replies 1 ·
Replies
1
Views
2K