Before starting: there are 2 surfaces along which we may have normal and frictional forces

1. Before starting: • there are 2 surfaces along which we may have normal and frictional forces • If there are no friction at all top box will stay in place while bottom moving to the left • If you are standing on bottom box, to you it will look like top box is moving to the right, that means friction acting on top is directed opposite • So frictional force acting on top box is opposite to its apparent motion • Using Newton’s 3rd law force acting on bottom box while it is rubbing against top is equal but opposite • If bottom box moves to the left then there will be a frictional force between box and table opposing the motion. Ffr AB -FfrAB Fapp T Ffr wA • Now about normal forces, again along 2 surfaces. • Normal force acting on top box coming from bottom box. • And according Newton’s 3rd law force acting on bottom box • Normal force acting on bottom box coming from the table • Now weight of the top box – it acts on the top box • Weight acting on bottom box • Force applied to bottom box • If top box is tied up, then you have to put tensional force on top box NAB -NAB N wB