Which of the two is the reason a block slides down a wedge?

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SUMMARY

The discussion centers on the mechanics of a block sliding down a wedge, specifically analyzing the forces at play. Participants clarify that the sliding motion is due to the component of gravitational force acting parallel to the slope, expressed as mg sin(theta). The normal force (N) and the gravitational force component perpendicular to the slope cancel each other out, resulting in a net force that is solely the parallel component of gravity. This understanding emphasizes that only one resultant force is responsible for the block's motion down the incline.

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  • Study the concept of free-body diagrams to visualize forces acting on objects.
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EddiePhys
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Is the reason the block slides down the plane that the resultant of the normal force N and mg acts along the plane causing it to slide or is it because of the component of mg parallel to the plane acting on the box i.e. mgsin(theta)
 
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Both are the same thing.
 
jbriggs444 said:
Both are the same thing.

Wait, what? How?
 
jbriggs444 said:
Both are the same thing.
Isn't N canceled out by mgcos(x)?
 
But both N and the component of gravity perpendicular to the slope are perpendicular to the slope.
 
jbriggs444 said:
But both N and the component of gravity perpendicular to the slope are perpendicular to the slope.
But in opposite directions, isn't it?

Pardon me but my mechanics suck
 
Right. They are in opposite directions and are equal. They add to a net of zero. All that is left after you add normal force plus gravity is the component of gravity parallel to the slope.

The resultant of normal force plus gravity is equal to mg sin theta.
 
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jbriggs444 said:
Right. They are in opposite directions and are equal. They add to a net of zero. All that is left after you add normal force plus gravity is the component of gravity parallel to the slope.

The resultant of normal force plus gravity is equal to mg sin theta.

Oh, I see. Thanks!
 
Perhaps make your drawing like this...

FBu5G.png
 
  • #10
Just to clarify, you do not have 3 forces acting on the block.
You can consider N + mg to be acting, or the resultant to be acting, but not both.
 
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