Stacked Blocks - Video Solution

A Video Solution to the Whiteboard: Stacked Blocks

[labibaraidah]

Sir, I just added the friction force between the two blocks too.Because when we will push the bottom block, it will feel some trouble moving because of the friction force in its top so we will have to minus that from the given force.Am I wrong?

[kingpusspuss]

How did you get (m1/m2 + 1) Fs 1(2) from the simplification on 6:14?

[hannahxie]

My lifesaver. THANK YOU SO MUCH. This is so clear

[paulie]

To make it simpler, the max force b4 m2 moves is equal to the friction force. So, the acceleration of m2 or the entire system a = (mu * m2 * g)/m2 = mu * g. Now, consider a force to move the entire system m1 & m2 with a (mu * g). Since there is no friction under m1 and (m1+m2) move together, we will get F = (m1 + m2) * a. If you substitute a with (mu * g), you will get the same answer (F) as shown in the clip.

[lockinatti]

"Any force larger than F_f_s_max overcomes the force of static friction and causes sliding to occur. The instant sliding occurs, static friction is no longer applicable" - Wikipedia. Im confused since the applied force F seems to be greater than F_f_s in your equation which would imply slipping right? I follow your logic but i don't understand how they ever move together without slipping because whatever force you apply to the bottom block will be completely apposed by friction until the force you apply becomes larger than F_s_max, at which point the bottom block will move but there will be slipping. My logic says if the bottom block is moving, there is slipping.

[sharminafroz]

Ur accent is not clear to me.. I am an indian sir.... 😣