What is the magnitude of the normal force in this block stacking scenario?

In summary, the question involves three blocks stacked on a frictionless surface, with masses of 37.0 kg, 18.0 kg, and 20.0 kg respectively. A downward force of 170 N is applied to the top block. Using the equation Fn + T + (-mg) = 0, we can determine that the normal force exerted by the bottom block on the middle block is 542.4 N.
  • #1
lacar213
29
0

Homework Statement


Three blocks are arranged in a stack on a frictionless horizontal surface. The bottom block has a mass of 37.0 kg. A block of mass 18.0 kg sits on top of it and a 20.0 kg block sits on top of the middle block. A downward vertical force of 170 N is applied to the top block. What is the magnitude of the normal force exerted by the bottom block on the middle block?



Homework Equations


Fn + T + (-mg) = 0


The Attempt at a Solution


20 + 18 = 38*9.8 = 372.4 N
Fn + 170 - 372.4 = 0
Fn = 202.4
 
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  • #2
lacar213 said:

The Attempt at a Solution


20 + 18 = 38*9.8 = 372.4 N
Good.
Fn + 170 - 372.4 = 0
Careful: That 170 N force acts downward.
 
  • #3
So the 170 needs to be negative .. ?
Fn + (-170) - 372.4 = 0
Fn = 542.4
 
  • #4
Looks good!
 

FAQ: What is the magnitude of the normal force in this block stacking scenario?

What is normal force?

Normal force is the force that a surface exerts on an object that is in contact with it. It is always perpendicular to the surface and acts to prevent the object from passing through the surface.

How is normal force calculated?

Normal force is calculated by multiplying the mass of the object by the acceleration due to gravity. This is because normal force is equal to the weight of the object, which is determined by its mass and the gravitational force acting on it.

What is the relationship between normal force and weight?

Normal force and weight are directly proportional to each other. This means that as the weight of an object increases, the normal force exerted by the surface also increases. If the weight of the object decreases, the normal force will also decrease.

Can normal force be negative?

No, normal force cannot be negative. It always acts in a direction perpendicular to the surface and is therefore always positive. If an object is on an inclined surface, the normal force may be less than the weight of the object, but it will still be a positive value.

What are some real-life examples of normal force?

Some real-life examples of normal force include: a book resting on a table, a person standing on the ground, a car on a flat road, or a bird perched on a branch. In all of these cases, the normal force is equal to the weight of the object and prevents it from falling through the surface.

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