- #1
Peter Lauer
- 2
- 0
Hey guys, My first post, I'm not sure this is the right place to put my question...but here it goes:
A block of mass m stands on another block of mass M. Some force F starts pushing M to the right, initially both blocks move together then, as F increases the block with mass m starts to slide to the left. There is no friction between the floor and block M, just between M and m.
The solution is given by the equations :
Friction = ma
F-Friction = MA
a,and A are the accelerations for blocks m and M respectively.
So, I don’t understand why the block m slides to the left. Because by Newton’s third law, if block M is pushed by some force, the way I see it, friction pushes back, so M pushes m forward to the direction of force F,as m pushes back. So why mass m is moving backwards ? I'm pretty sure my application of the Third Law is wrong but why? The only way m could possibly go to the left, would be if M pushed m back then m would have no option but push M forward so the equations should be :
Friction = ma
F+Friction = MA
So what's wrong?
A block of mass m stands on another block of mass M. Some force F starts pushing M to the right, initially both blocks move together then, as F increases the block with mass m starts to slide to the left. There is no friction between the floor and block M, just between M and m.
The solution is given by the equations :
Friction = ma
F-Friction = MA
a,and A are the accelerations for blocks m and M respectively.
So, I don’t understand why the block m slides to the left. Because by Newton’s third law, if block M is pushed by some force, the way I see it, friction pushes back, so M pushes m forward to the direction of force F,as m pushes back. So why mass m is moving backwards ? I'm pretty sure my application of the Third Law is wrong but why? The only way m could possibly go to the left, would be if M pushed m back then m would have no option but push M forward so the equations should be :
Friction = ma
F+Friction = MA
So what's wrong?