The weight of the block in the drawing is 70.5N. The coefficient of static frict
ID: 1694096 • Letter: T
Question
The weight of the block in the drawing is 70.5N. The coefficient of static friction between block and the vertical wall is 0.4 and the Force F is at 40o a) what minimum force F is required to prevent the block from sliding down the wall b) What minimum force is required to start the block moving up the wall.The weight of the block in the drawing is 70.5N. The coefficient of static friction between block and the vertical wall is 0.4 and the Force F is at 40o a) what minimum force F is required to prevent the block from sliding down the wall b) What minimum force is required to start the block moving up the wall.
Explanation / Answer
a) The equation of motion in this case is mg + F cos40 = fk ==> F cos40 = fk - mg ==> F cos40 = - uk F sin40 - mg ==> F [ cos40 + uk sin40] = - mg ==> F = - m g / [ cos40 + uk sin40] = - 70.5 / [0.7666 + 0.4 * 0.642] = - 68.86 N Here negative sign indicates force applied in opposite direction to the motion of block. b) In this case equation of motion is F cos40 + fk = mg ==> F cos40 - uk F sin40 = mg ==> F = mg / [ cos40 - uk sin40] = 138.28N
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