a book weighs 4 N. When held at rest in your hands, the net force on the book?

0N

To determine the net force on the book when held at rest in your hands, we need to understand the concept of equilibrium.

When an object is at rest or in uniform motion, it is said to be in equilibrium. In equilibrium, the forces acting on the object are balanced, resulting in a net force of zero.

In this case, since the book is held at rest in your hands, it is not accelerating. Therefore, the net force on the book must be zero.

To calculate the net force on the book, we can consider the forces acting on it. The only force acting on the book is its weight, which is equal to its mass multiplied by the acceleration due to gravity. The weight of an object can be calculated using the formula:

Weight = mass x acceleration due to gravity

Given that the weight of the book is 4 N, we can rearrange the formula to solve for mass:

Mass = Weight / acceleration due to gravity

Given that the acceleration due to gravity is approximately 9.8 m/s², we can substitute the values into the formula:

Mass = 4 N / 9.8 m/s² ≈ 0.41 kg

Now, since the book is at rest, the net force on it is zero. Therefore, the force exerted by your hands must be equal in magnitude and opposite in direction to the weight of the book (4 N).

So, the net force on the book, when held at rest in your hands, is 4 Newtons in the upward direction (opposite to the force of gravity).