Understanding Normal Force in a Vertical Spring System

[Leong]

Homework Statement

A vertical spring is fixed on a table. A book is put on the spring. The book compresses the spring until static equilibrium is reached. Question: Is there a normal force exerted by the spring on the book? Why or why not?

Homework Equations

The Attempt at a Solution

I think there is because normal force is a contact force. As long as two bodies are in contact, I think it exists. But I never see books mention normal force in this kind of problem.

 

[NascentOxygen]

Hi Leong. What do you understand by the meaning of the word "normal" here?

 

[Leong]

Perpendicular

 

[Doc Al]

If you put the book on a table, would there be a 'normal' force supporting it? It's the same idea here. The term 'normal force' is commonly used to describe the support force on an object from some surface. (Imagine the top of the spring has a platform for resting the book on.)

 

[Aditya3003]

Let the mass of the book be 'm' and the spring constant be 'k'. When the book has achieved static equilibrium we know two things.
1) The force of gravity is trying to pull the book downwards. This force = m*g ( g is the gravitational constant for Earth and equals 9.81m per second squares )
2) There has to be a force which cancels the force of gravity otherwise the book will start accelerating under the influence of unbalanced force.

Now, the spring will definitely have to exert a force on the book because it is at rest and gravity acts towards the center of Earth (i.e. downwards towards the table). The spring applies a force which equals mg in order to cancel the force of gravity.

Hope this Helped

 

[Leong]

If you put the book on a table, would there be a 'normal' force supporting it? It's the same idea here. The term 'normal force' is commonly used to describe the support force on an object from some surface. (Imagine the top of the spring has a platform for resting the book on.)

If there is no platform, just the book on the spring, will there still be a normal force on the book other than spring force and the weight of the book?

 

[Leong]

Let the mass of the book be 'm' and the spring constant be 'k'. When the book has achieved static equilibrium we know two things.
1) The force of gravity is trying to pull the book downwards. This force = m*g ( g is the gravitational constant for Earth and equals 9.81m per second squares )
2) There has to be a force which cancels the force of gravity otherwise the book will start accelerating under the influence of unbalanced force.

Now, the spring will definitely have to exert a force on the book because it is at rest and gravity acts towards the center of Earth (i.e. downwards towards the table). The spring applies a force which equals mg in order to cancel the force of gravity.

Hope this Helped

Do you mean spring force or normal force or both as the force on the book exerted by the spring on the book?

 

[Doc Al]

If there is no platform, just the book on the spring, will there still be a normal force on the book other than spring force and the weight of the book?

The spring force is the normal force.

Do you mean spring force or normal force or both as the force on the book exerted by the spring on the book?

The upward force that the spring exerts on the book to support it is the normal force. And that force is given by Hooke's law, since it is a spring.

There are only two forces acting on the book: The downward force of gravity and the upward force of the spring (which you can call the normal force, if you like).

 

[Leong]

The spring force is the normal force.


The upward force that the spring exerts on the book to support it is the normal force. And that force is given by Hooke's law, since it is a spring.

There are only two forces acting on the book: The downward force of gravity and the upward force of the spring (which you can call the normal force, if you like).

Thanks for the explanation which I cannot find anywhere. Thanks to everyone who replied to my post.