What Is a Normal Force? | Physics - Forces & Newton's Laws

[@physicslab42]

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[@aayushbhandari8377]

here are a few questions from my side: 1. 5:37 is the normal force on block A by block B F1-F2, and the normal force on block B by block A F2-F1 ? since the directions are opposite and equal? 2. what happens to the normal force between the blocks when the blocks accelerate, lets say to the right, with same magnitude ? i am confused on whether there will exist a normal force between the two blocks when in motion. 3. in general, is the magnitude of the normal force (horizontal) between two bodies in contact the difference between the forces acting on them. 4. you said that the normal force on a body is always normal to the surface. so we can take the normal force by a book on a table and the force by the table on the book as equal and opposite, right ? so can the same logic also be applied in the case of the two bodies in contact ? please do answer. please love from nepal

[@physicslab42]

Thanks for the questions! 1. In this scenario, we're not told whether the blocks are accelerating or not. For each block, the net horizontal force is equal to its own mass times its acceleration (Newton's 2nd law, Fnet=ma). If the blocks are not accelerating then F1=F2, Fn(B on A)=F1, and Fn(A on B)=F2. And it's always true that Fn(B on A)=Fn(A on B) because they're a pair of equal and opposite forces. 2. If F1 or F2 was greater than the other then the blocks will accelerate together at the same rate, and the relationship between the horizontal forces will depend on masses of block A and block B. There will still be a normal force between the blocks when accelerating, and they will always be equal to each other. However, if we removed F1 and F2 then there is nothing pushing the blocks into each other and there would not be a normal force between the blocks. There would be a normal force if only F1 or F2 was still acting on the blocks, causing one block to accelerate the other block. 3. In order to figure out how the normal force between two bodies is related to the other forces, you need to write out Newton's 2nd law (Fnet=ma) in the horizontal direction. The relationship between the forces will depend on the acceleration and the masses. 4. Yes a normal force is always normal (perpendicular) to the contact surface between the two objects. So the normal force by a book on a table is equal in magnitude and opposite in direction to the normal force by the table on the book. This is true for any two bodies that are in contact. I hope this helps!

[@aayushbhandari8377]

@@physicslab42 yes, it helped. thanks.