Question
numbers. 1. Note the following situations: is not to C'ase 1 C'ase 2 Case 3 hers. For In which case will the magnitude of the normal force on the block be equal to (Mg + F sin )? A) both cases 1 and 2 B) both cases 2 and 3 C) cases 1, 2, and 3 D) case 1 only E) case 2 only the train 2. A 20-kg block is pushed against a vertical wall by a horizontal force of 150 N as shown in the figure. The coefficient of static friction, s between the block and the wall is 0.65: and the coefficient of kinetic friction, k, is043) which one of the following statements is true, if the block is initially at rest? A) The total force exerted on the block by the wall is directed horizontally. B) The block will slide down the wall because the coefficient of kinetic friction is less than the coefficient of static friction. st law is C) The block slides down the wall with an acceleration of magnitude 6.58 m/s em and etween es the er the D) The block will slide down the wall because the force of static friction can be no larger than 64.5 N E) The block will remain at rest because the coefficient of static friction is greater than the coefficient of kinetic friction. 9 No 150 N 20 k
Explanation / Answer
1) option d is correct.
Force F pushes the block towards the ground, so normal increases. In second case, it becomes less than mg.
In case 1, N = mg + F sin theta
In case 2, N = mg - F sin theta
In case 3, N = mg cos theta
