Identifying the Forces Acting on a Box: A, B, C, D, E?

In summary, the forces acting on the box in this scenario are the gravitational force (box's weight), the force of the floor on the box (normal force), and the force of Bob on the box. It is important to only include forces that act on the object and not the forces that the object exerts on others, as shown in a free body diagram.
  • #1
ysk1
32
1
Question:

Bob is applying a horizontal force to a box across a level floor. The box can slide across the floor without friction.

Identify the forces acting on the object of interest. From the list below, select the forces that act on the box.

A. gravitational force acting on the box (box's weight)
B. force of the floor on the box (normal force)
C. force of the box on the floor
D. force of Bob on the box
E. force of the box pushing on Bob






I know that A, B, and C are true, but I'm confused of D and E.
In free body diagram, do you also include Newton's 3rd law, which is D and E?

Thank you.
 
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  • #2
ysk1 said:
I know that A, B, and C are true, but I'm confused of D and E.
In free body diagram, do you also include Newton's 3rd law, which is D and E?
Careful! The key to a proper free body diagram for the box is to show all forces acting on the box and only those forces. The fact that the box, via Newton's 3rd law, also exerts forces on other objects is irrelevant. (They may be important for another part of the problem, of course.)

Better rethink your answers.
 
  • #3
Do I include only the forces that act ON the object, but not the forces that the object exerts on others?
Considering that, I think the correct answers are A, B, and D?
Am I correct?
 
  • #4
ysk1 said:
Do I include only the forces that act ON the object, but not the forces that the object exerts on others?
Exactly.

Considering that, I think the correct answers are A, B, and D?
Am I correct?
Yes you are.
 
  • #5
Now I have a clear grasp of drawing the free body diagram.
Thank you so much for your help. :smile:
 

1. What are the five forces acting on a box?

The five forces acting on a box are A) weight, B) normal force, C) friction, D) applied force, and E) tension.

2. How do you calculate the weight of a box?

The weight of a box can be calculated by multiplying its mass by the acceleration due to gravity, which is typically 9.8 m/s^2 on Earth.

3. What is the normal force and how does it affect a box?

The normal force is the force exerted by a surface on an object that is in contact with it. In the case of a box, the normal force is equal in magnitude and opposite in direction to the weight of the box. It keeps the box from falling through a surface or object.

4. How does friction affect a box?

Friction is a force that opposes motion between two surfaces in contact. In the case of a box, friction can either help or hinder its movement depending on the direction and magnitude of the applied force. If the applied force is greater than the force of friction, the box will move. But if the force of friction is greater, the box will not move.

5. What is tension and how does it apply to a box?

Tension is a pulling force that is transmitted through a rope, cable, or similar object. In the case of a box, tension can be applied to move it in a specific direction. For example, pulling a box with a rope will create tension in the rope, which will then be transmitted to the box and cause it to move.

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