Advantage of doorknobs with long handles

  • Thread starter Thread starter deamonvivid
  • Start date Start date
Click For Summary

Homework Help Overview

The discussion revolves around the advantages of doorknobs with long handles compared to standard round ones, specifically in relation to torque and force requirements. Participants explore the concept of torque and its implications in practical scenarios.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the definition of torque and its relationship to force and distance from the axis of rotation. They question how changes in the radius affect the force needed to achieve the same torque.

Discussion Status

The discussion is active, with participants clarifying definitions and exploring the implications of torque in practical applications. Some have provided insights into the relationship between force and radius, while others are confirming their understanding of the concepts discussed.

Contextual Notes

There is a mention of the axis of rotation being at the hinges, which raises questions about the assumptions made in the context of doorknob design.

deamonvivid
Messages
10
Reaction score
0
Torque question.
What is the advantage of of doorknobs with long handles instead of standard round ones in terms of decreased force requirements?
 
Physics news on Phys.org
deamonvivid said:
Torque question.
What is the advantage of of doorknobs with long handles instead of standard round ones in terms of decreased force requirements?

What is the definition of torque?
 
the rotational motion of an object
 
deamonvivid said:
the rotational motion of an object

True.. more specifically, how is that rotational motion caused?

What is the equation for torque?
 
deamonvivid said:
the rotational motion of an object

There is a definition of torque that is related to force and the distance from the rotation-axis that the force was applied...
 
rFsin()
 
the lever arm is the perpendicular distance from the axis of rotation to the line of action of the force
 
thats what you talking about right
 
deamonvivid said:
rFsin()

yes, exactly... so suppose I apply a certain torque with a certain force F1 at a radius r1... but then I double my r from r1 to 2r1... how much force do I need for the same torque as before (keeping the same angle)...
 
  • #10
deamonvivid said:
thats what you talking about right

yes exactly.
 
  • #11
twice the force as well
 
  • #12
oops, a smaller force
 
  • #13
deamonvivid said:
oops, a smaller force

exactly... only half the force is needed for the same torque...
 
  • #14
deamonvivid said:
oops, a smaller force

Right. Apply this knowledge to your practical usage of doorknobs, the lever one VS. the turning one.
 
  • #15
but i was thinking wasn't the axis of rotation always been considered was at the hinges
 
  • #16
Ok! got it now.
 
  • #17
deamonvivid said:
Ok! got it now.

cool.
 
  • #18
Thanks.
 
  • #19
lol.. real time replying is awesome
 
  • #20
deamonvivid said:
Thanks.

no prob.
 
  • #21
l46kok said:
lol.. real time replying is awesome

lol. yup.
 

Similar threads

Mechanical Advantage on Gym Machines
  • · Replies 3 ·
Replies
3
Views
1K
High School Hold a hammer at the top vs bottom of the handle
  • · Replies 7 ·
Replies
7
Views
2K
Rotational Dynamics on a door knob
  • · Replies 3 ·
Replies
3
Views
5K
Frequency & Wavelength of a Vibrating Wire
  • · Replies 5 ·
Replies
5
Views
2K
Mechanical Advantage in a crank system
  • · Replies 26 ·
Replies
26
Views
9K
Calculating Tangential Force for Grindstone Rotation
  • · Replies 27 ·
Replies
27
Views
7K
Graduate Torque and Moment of Inertia of a Lever Arm
  • · Replies 2 ·
Replies
2
Views
4K
How Long Does It Take for a Handle to Become Unbearably Hot?
  • · Replies 3 ·
Replies
3
Views
2K
Answer: Calculate Torque: 0.8 Nm
  • · Replies 41 ·
2
Replies
41
Views
11K
Undergrad 1:1 versus 2:1 Mechanical Advantage debate
  • · Replies 20 ·
Replies
20
Views
2K