Find Force Req'd to Move Object: Weight & Calc Mu=F/Normal Reaction

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Discussion Overview

The discussion revolves around understanding the force required to move a stationary object, specifically focusing on the concepts of weight, mass, and friction. Participants explore the relationship between these concepts and the formulas involved, particularly the equation mu = F/Normal Reaction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on whether to use the weight of a person (40 kg) multiplied by gravitational acceleration (9.81) or just the mass (40 kg) when calculating force.
  • Another participant defines mass as being in kg and weight as mass multiplied by gravitational acceleration, expressed in Newtons.
  • A question is raised about the terminology of weight versus mass, particularly in the context of a 50 kg object placed on a table, and whether this should be considered as 50 kg or as a force of 50 x 9.81 kgf.
  • One participant explains that in physics, weight refers to the gravitational force acting on an object, which is measured in Newtons, and notes the historical context of the Newton unit.
  • Another participant emphasizes that weight is mass times gravitational acceleration and points out that saying something has a weight of 50 kg is technically incorrect, providing an example of how to calculate weight in Newtons.
  • Discussion includes the force required to accelerate a bike and rider, noting that this is the combined mass times acceleration, and mentions the effects of air resistance and friction.

Areas of Agreement / Disagreement

Participants express differing views on the terminology and definitions of weight and mass, with some clarifying the distinction while others question the usage. The discussion remains unresolved regarding the proper application of these concepts in calculations.

Contextual Notes

There are unresolved assumptions regarding the definitions of weight and mass, as well as the application of gravitational acceleration in different contexts. The discussion also highlights potential confusion stemming from historical terminology changes.

satishinamdar
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I want to know the fundamentals of finding the force reqd for moving a stationary object such as a car or a segway (which has got two wheels).
Also let me know in a formula mu = F/ NORMAL REACTION,
WHAT IS THE VALUE OF A WEIGHT HAS TO BE TAKEN?
meaning if weight of a person standing on a pedal of a bicycle is 40 kg then should I multiply with 9.81 ? or should I use figure of 40 alone?
 
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Mass = in kg.
Weight = mass x gravitational acceleration, in Newtons.
 


when we say a weight of 50 kg is kept on a table, then is it 50 kg ? and force applied vertically down is 50x9.81 kgf?In earlier days this Newton unit was not there , it is confusing.pl help.
 


The layman's term for weight is mass in physics. Both of these are in kg.
Weight in physics is the attractive force on the object by our Earth (or whatever planet you are on). This is in Newtons.

Also, the Newton unit has been around for... ~300 years? :)
 


Weight is mass times the acceleration due to gravity. The acceleration due to gravity is almost the same everywhere on the surface of the earth, which is why people say weight when they actually mean mass.

e.g. If a mass of 50kg is kept on a table, then the weight of that mass is roughly 500Newtons (which equals the force down on the table).
Saying that something has a weight of 50kg is technically wrong.

Also, the force required to accelerate the bike+person is simply the mass of the bike+person times the acceleration.

The reason you need to keep pedalling to keep the bike at constant speed is because of air resistance. Friction with the road does not act to slow the bike (as long as the wheels don't slip).
 

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