Suppose on a 2D plane a person pushes a refrigerator to the right. The only reason they are able to do that is due to the presence of frictional force. Normally if we look at the shoes of the person, the frictional force would be to the right since the person's shoes would naturally want to move to the left as pushing the refrigerator to the right. However, we know that frictional force opposes motion, and the person moves to the right because they are pushing the refrigerator to the right. So wouldn't it also make sense that the frictional force is to the left as well?
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$\begingroup$ Re, "frictional force opposes motion," Dynamic friction opposes motion, but in this case, you probably are talking about static friction. Dynamic friction is the force between the shoes and the floor when the shoes are slipping. Static is when the shoes grip the floor and do not slip. $\endgroup$– Solomon SlowCommented Dec 24, 2022 at 19:49
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3 Answers
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So wouldn't it also make sense that the frictional force is to the left as well?
No. Kinetic (sliding) friction would be acting to the left if the person were sliding to the right. But any sliding/slipping will occur to the left because the refrigerator is exerting a force on the person to the left per Newton's 3rd law.
But the friction that enables the person to push the refrigerator to the right without slipping to the left is static friction acting towards the right.
Hope this helps.
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Frictional force opposes relative motion at the point of contact.
The motion of the mover's torso is not directly relevant since it is not in sliding contact with any surface. The motion of the sneakers on the floor is.
As you've determined, without friction present between the shoes and the floor, the shoes would be accelerated to the left by the person pushing against the object. Friction (to the right) prevents this.
answered Dec 24, 2022 at 19:34
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Suppose on a 2D plane a person pushes a refrigerator to the right.
There are two frictional forces which relate to the fridge:
The frictional force on the fridge to the left due to the ground.
The frictional force on the ground to the right due to the fridge.
There are two frictional forces which relate to the person pushing the fridge:
The frictional force on the ground to the left due to the person.
The frictional force on the person to the right due to the ground.$\,\,\bf\large*$
$\bf\large*\,\,$ If that force was absent the person could not move the fridge by pushing it.
