Calculating Force to Move Block Horizontally - Abraham

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Discussion Overview

The discussion revolves around calculating the force required to move a block horizontally on a table, considering the effects of friction. Participants explore the relationship between applied force, friction, and acceleration, while addressing the implications of different scenarios, such as movement on a surface versus in free space.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Abraham introduces the problem of moving a 25N block horizontally with a 30N force and seeks to determine if this force is sufficient.
  • Vidar notes that if 30N is needed to maintain constant velocity, friction must be considered, complicating the calculation of acceleration.
  • Another participant suggests using a coefficient of friction of 0.4 to calculate the maximum static friction force to determine if the applied force is adequate to initiate movement.
  • One participant asserts that friction assists in movement, while another clarifies that friction actually retards movement, emphasizing its role in preventing motion unless overcome.
  • There is a discussion about the nature of friction in free space, with one participant mistakenly suggesting it is non-zero, while others clarify that friction is zero in such conditions.
  • Participants discuss the calculation of maximum friction force using the coefficient of friction and the normal force, indicating that this force determines the minimum required pulling force to initiate movement.

Areas of Agreement / Disagreement

Participants express differing views on the role of friction in movement and its implications in different scenarios. There is no consensus on the calculations or the effects of friction in various contexts.

Contextual Notes

Participants rely on assumptions regarding the coefficient of friction and the conditions of movement, which may not be fully defined or agreed upon. The discussion includes unresolved aspects of acceleration and the exact nature of forces involved.

abrahamjp
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Hi,

Consider a block sits on a table and its weight is 25N.So its weight is acting downwards
and I want to move this block horizontally and I am applying a force of 30N.

How I can calculate whether with this Force body moves?

Cheers

Abraham
 
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If you use 30N of force to move the block at constant velocity, there is friction between the table and the block that is the cause of necessary force. If you must apply 30N to make it move in the first place, some of that force is used to accelerate the block. Hard to say what the acceleration is until the block moves at constant velocity. Also hard to calculate this as both acceleration and friction are unknown.

Vidar
 
Hi,
If I take coificient of friction as 0.4 for wood table.
But I am not getting acceleration figure.I just want to move it from rest
and use a force by pushing it with hand.
 
abrahamjp said:
Hi,
If I take coificient of friction as 0.4 for wood table.
But I am not getting acceleration figure.I just want to move it from rest
and use a force by pushing it with hand.
Use the coefficient of friction to calculate the maximum value of static friction. That will tell you if your 30 N force is sufficient to get it moving.
 
So friction helps in movement,right?If my block would have been in free space compared to resting on a table with 0.4cof-->pulling force reuired is 0.4 times less than that in free space.
 
Friction acts to retard movement. If friction acted otherwise, nothing could ever stay still.
 
right.Friction in free space is ZERO,I was thinking it is 1.
 
Instead of friction, perhaps you were thinking of sliction.
 
lol. As Doc Al was saying, you can calculate the max friction force, using the coefficient of friction and the normal force (weight, in this case). This max friction force is the minimum pulling force to cause movement of the block, because the friction force will take whatever value is necessary to stop movement. (until its max value is reached, in which case it will still oppose movement, but will not be enough to stop movement from happening). In free space, there is no friction, so the minimum pulling force is zero (as you would expect).
 

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