Understanding Work Against Friction in Physics

[Josielle Abdilla]

When we say the work done against friction, what do we mean by that? This concept is really worrying me.Thanks in advance!

 

[Wrichik Basu]

It means the work done to overcome friction. As you must be knowing, friction is always present, and some work has to be done to start motion or to keep the motion uniform. That very work done is termed as "wirk done against friction".

 

[PeroK]

When we say the work done against friction, what do we mean by that? This concept is really worrying me.Thanks in advance!

When you move something that has a resisting force, like friction, then not all the energy you put in (work done) goes to kinetic energy. Some of the energy is lost to friction and dissipated as heat. That is called work done against friction.

 

[sophiecentaur]

When we say the work done against friction, what do we mean by that? This concept is really worrying me.Thanks in advance!

Friction (like Electrical Resistance) is never a source of Energy; it describes an energy loss mechanism. So we say you have to work 'against it'. The work done is the Friction Force times the Distance that the surfaces move (slip) relative to each other.
There can be confusion when you consider the friction between the driving wheels of a car. In that case, the friction force between tyre and road is used to push the car forward. If the tyres/road are ideal then there will be no slipping and no energy will be lost (never happens in practice) and all the power is transferred usefully.
A useful bit of advice is to try to avoid worrying too much about the words that some people use to describe Physics processes. They are often applied differently from the way they're used in everyday language. Try to stick to what the Mathematical Formula are telling you and you will not go wrong. (Well - not so much, at least!)

 

[Josielle Abdilla]

Thanks a lot. Besides that, what does it mean when an object overcomes the inertial mass, in order to accelerate?

 

[sophiecentaur]

Thanks a lot. Besides that, what does it mean when an object overcomes the inertial mass, in order to accelerate?

I would say that the expression is from the Eighteenth Century. It gives the impression that things have to be 'got going' before they accelerate because of their mass. F=Ma applies for all velocities, however low, as long as friction or other static forces, like a rope restraint are not involved. The statement is, presumably mistakenly related to the sometimes very small effect of static friction just before things get moving and can easily be due to their Mass. i.e. high mass has high weight so a high static friction force will be 'related to' Mass but it's not related to Inertia. In fact, I do not like the term Inertia - certainly not in Newtonian Mechanics. Mass and Momentum seem to be adequate (and defined) terms to describe those rather arm-waving effects that are sometimes put down to the effect of Inertia. Afaiac, inertia is what prevents us from getting down to work and is not a good physical reason for a restriction of movement.
If you can't find an equation in your textbook that includes a variable Inertia (and I'd bet you can't) then try to avoid the term.

 

[Josielle Abdilla]

Thanks a lot but do you have to overcome the inertial mass to accelerate? Or to move at constant velocity?

 

[sophiecentaur]

Thanks a lot but do you have to overcome the inertial mass to accelerate? Or to move at constant velocity?

Where does the term "overcome" come into it? Newton's First and Second Laws of Motion state the situation very adequately. A Force is necessary to produce acceleration - and the net force needed to produce a given acceleration is proportional to the Mass (even as the Mass or Velocity approach zero). The distinction between Inertial and Gravitational Mass is how they relate to Non Gravitational and Gravitation forces. In our system of units, the two masses measure the same.
From your original question, with category B, I was making assumptions about your level of Physics knowledge. There is a good reason why the two kinds of mass are not treated as distinct in High School; it's a needlessly hard can of worms to discuss so the question need not be asked.

 

[Josielle Abdilla]

I have only just started physics at advanced a few month's ago and pir physics teacher mentioned about inertial mass

 

[sophiecentaur]

I have only just started physics at advanced a few month's ago and pir physics teacher mentioned about inertial mass

But do you take my point about "overcome"? I would say that a totally linear relationship does not imply any threshold / overcoming value. The result is just proportional and exactly what you would expect, for a given number of kilograms, whether those kg were measured with a set of lab scales or in a rocket with a known acceleration. The 'difference' between the two masses is a very esoteric one and you'd need to have been introduced to GR at a reasonable level before it would be relevant. I'd bet that Newton would have had a useful conversation about it of course (smart cookie that he was) but he wouldn't have acknowledged any 'threshold' effect of a force.