What is the direction of forces exerted on a plank by a wall in statics?

In summary, the conversation involves a discussion of a problem related to statics and determining the direction of forces on a wall. One person believes the statement is true based on the use of \sumFy = 0, but the other person gives a hint to consider the forces at a specific point to determine the correct direction of forces.
  • #1
nahanksh
41
0

Homework Statement


http://online.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys211/oldexams/exam3/sp08/fig15.gif

The force exerted on the plank by the wall is upwards. (True/False)


Homework Equations





The Attempt at a Solution



In statics, when using [tex]\sumFy = 0[/tex], i thought the forces exerting on the wall should cancel the force of gravity (weight : mg).. That's the reason why i thought the statement to be TRUE. But it's actually FALSE...

How to decide the direction of forces?
(I am always confused with this..)

Please could someone help me out here?
 
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  • #2
Hi nahanksh! :smile:
nahanksh said:
In statics, when using [tex]\sumFy = 0[/tex], i thought the forces exerting on the wall should cancel the force of gravity (weight : mg).

But you're forgetting the force from the pointy thingy … that's three forces that have to cancel, and you have no idea what that extra force is.

Hint: when you don't know what a force is, and you don't want to know, always take moments about a point which you choose so that that force has zero moment. :wink:
 
  • #3
I don't quite get the hint you have given...

Are you saying that there is both horizontal and vertical forces in the point thing?
(Then, the answer is FALSE because it has upward AND downward forces?)

I am so confused...T_T
 
  • #4
nahanksh said:
Are you saying that there is both horizontal and vertical forces in the point thing?

Hi nahanksh! :smile:

(just got up :zzz: …)

I'm not interested in the forces at the point thing.

Just follow my hint! :wink:​
 
  • #5
tiny-tim said:
Hi nahanksh! :smile:

(just got up :zzz: …)

I'm not interested in the forces at the point thing.

Just follow my hint! :wink:​

I don't understand still...

We ARE interested in the point thing because it's only point related to the WALL..

How do we know the direction of the forces by the wall without considering that point..?

Please give me a little bit more of a hint...
 
  • #6
nahanksh said:
How do we know the direction of the forces by the wall without considering that point..?

By taking moments about that point, so that the force at that point is multiplied by zero.
 

FAQ: What is the direction of forces exerted on a plank by a wall in statics?

What is statics and how does it relate to exerting forces?

Statics is the study of objects that are at rest or moving at a constant velocity. This includes the analysis of forces acting on an object and the effects of these forces on its motion. In terms of exerting forces, statics helps us understand how different forces interact with each other and how they affect the equilibrium of an object.

What are the different types of forces that can be exerted?

There are four main types of forces that can be exerted on an object: tension, compression, shear, and torsion. Tension is a pulling force, compression is a pushing force, shear is a force that causes one part of an object to slide against another part, and torsion is a twisting force.

How do we calculate the magnitude and direction of forces in statics?

In statics, we use Newton's laws of motion and vector analysis to calculate the magnitude and direction of forces. By breaking down a force into its components and applying the principles of equilibrium, we can determine the net force acting on an object.

What is the significance of the center of gravity in statics?

The center of gravity is the point at which the weight of an object is concentrated. In statics, the center of gravity is important because it helps us understand the stability of an object. An object will remain stable as long as its center of gravity is directly above its base of support.

How do we apply the principles of statics in real-life situations?

Statics is applicable in a wide range of real-life situations, such as building structures, designing bridges, and analyzing the stability of vehicles. By understanding the forces acting on an object and how they affect its motion, we can make informed decisions in engineering and design to ensure safety and efficiency.

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