Normal Force Between Block & Table: Free Body Diagram Explained

In summary, a block resting on a table has a normal force equal to its weight, and this force depends on the angle of the table with the horizontal.
  • #1
starbaj12
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If there was a block on a table what would be the normal force between the block and the table. If you could describe the free body diagram that would be great too.
 
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  • #2
The normal force between the block and the table is just the weight of the block.

A "free body diagram" would show the weight vector of the block acting downward on the table and an equal force vector acting upward on the block.
 
  • #3
normal force

Assuming that the only other important force acting on the block except normal reaction is the force of gravity, then the normal force depends upon the angle of the table with the horizontal.

In the most probable case when the angle is 0 deg., the normal reaction is equal to the force of gravity in magnitude (but upwards), not because of Newton's third law but because of Newton's first law. Since, the block is not accelerating, forces on it must be balanced, so normal force has to be equal to the force of gravity.

In case the table is at an angle, normal recation is equal in magnitude to the component of gravity opposite to it.

spacetime
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  • #4
I just wanted to say an important fact about the free body diagram, that makes students confused:
Just put the forses that ACTs on the specified body and not more!
It may seem very simple, but I have seen lots of mistakes about it.
Good Luck!
 
  • #5
starbaj12 said:
If there was a block on a table what would be the normal force between the block and the table. If you could describe the free body diagram that would be great too.
Assuming the ordinary situation, a block resting on a horizontal table, then a free body diagram of the block would show:
- its weight acting down (agent = the earth)
- the normal force acting up (agent = the table)

Since we know the block is in equilibrium, the magnitude of the normal force must equal the block's weight.

So far, none of this has anything to do with Newton's Third law. Did you have a question about it?
 

1. What is a free body diagram?

A free body diagram is a visual representation of all the forces acting on an object. It includes all the external forces, such as gravity or friction, that are acting on the object, and is useful for understanding the overall motion of the object.

2. How is the normal force between a block and table determined?

The normal force is the force exerted by a surface on an object that is in contact with it. In the case of a block resting on a table, the normal force is equal in magnitude and opposite in direction to the weight of the block, and is determined by the force of gravity on the object.

3. What factors affect the normal force between a block and table?

The normal force is affected by the weight of the object, the angle at which it is placed on the surface, and any other external forces acting on the object, such as friction or applied forces.

4. Why is the normal force important in understanding the motion of an object?

The normal force is important because it is one of the forces that determines the overall motion of an object. It can influence the acceleration, velocity, and direction of the object, and is crucial in analyzing the forces acting on an object in equilibrium.

5. How is the free body diagram used to solve problems involving the normal force?

The free body diagram is used to identify and represent all the forces acting on an object, including the normal force. By labeling and analyzing the forces, one can use equations such as Newton's laws of motion to solve for the unknown variables and understand the overall motion of the object.

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