00:01
And this problem, we have a book that's being pushed by both sides by two hands.
00:05
And we're given the weight of the book, which is 31 newtons, and the coefficient of static friction between the hand and the book is 0 .4.
00:17
And we want to calculate the minimum force required to keep the book from falling out of the hands.
00:24
So to do this problem, we need to draw a free body diagram to show the forces acting on the book.
00:30
That we can set up newton's second law, which is the sum of the forces equals mass times acceleration.
00:38
And we'll be interested to look into the forces in the y -axis because that's the direction that the book will fall if there's not enough force.
00:48
So if you draw a free body diagram, we have the force of one hand if we're looking at one side, going to the right.
00:59
And since it's a contact force, the book will exert a force in the opposite direction of the hand called the normal force.
01:08
In the y -axis, we have the weight going down, the weight of the book.
01:15
And what's keeping the book from falling is the static frictional force acting in the opposite direction, the weight.
01:22
And so what we want to calculate is this force, the normal force, because this will be the same magnitude as the force.
01:31
Of the hands...