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When a body topples about a point, I'm clear about the net torque acting on the body, just wondering if the toppling can happen if there is no friction or not enough friction; can there be a situation when the point of contact of the body with the ground slides and the body still topples ?

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Yes you can tip an object that is sitting on a frictionless surface. Let me show you how.

Consider first the case where the object is in a vacuum in free space. To create rotation I need to apply a torque to the object. Consider now that if I push the object anywhere other than the center of mass. For example, visualize a bar where I am pushing sideways at one end. The object will begin to rotate about the center of mass since the side with more mass resists my push more than the one with less.

Now back to your question. If you push an object at the center of mass while it is on a frictionless surface it will only slide and will not topple. However, if you push it away from the COM then as above there is a torque and the object can topple.

Note that these are not exclusive though, the object could start sliding and then topple or could start to slant over but then just slide upon finding a new balance point. It all depends on the specifics of the problem beyond the simple thought experiment above.

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  • $\begingroup$ "the object could start sliding and then topple or could start to slant over",can both sliding and toppling happen at the same time. $\endgroup$
    – sachin
    May 11, 2018 at 19:15
  • $\begingroup$ Yes. Consider the frictionless case. There is nothing stopping the translational motion of the com so it it sliding but at the same time toppling if you push it away from the position of the com. Toppling and sliding are just terms we use to describe the rotational motion vs the translational motion. $\endgroup$
    – fhorrobin
    May 11, 2018 at 19:17
  • $\begingroup$ If the force is applied from the left side on a block and the block both slides and topples,will the sliding take place towards right side or towards left side. $\endgroup$
    – sachin
    May 11, 2018 at 19:20
  • $\begingroup$ Think about it this way: the sliding is the motion that the object aquifer from the translation of the center of mass as if it were a point particle. So if we apply a force towards the left the object will move translationally or "slide" to the left as it must by Newtons 2nd law (if the net force is to the left the object will accelerate towards the left and in the no friction or low friction case there is clearly net force to left.) The toppling may also happen here and is based on the rotational motion. It's important to notice you can for most practical purposes treat them indeoendently. $\endgroup$
    – fhorrobin
    May 11, 2018 at 19:25

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