Newton's Second law: Pushing the box

  • Thread starter aatari
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  • #1
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Can someone please help me solve this question below.

1. Homework Statement

How much force is needed to push a 20 kg box across a floor at a constant speed of 0.5 m/s [forward] against a frictional resistance of 4 N?

Homework Equations


Fnet = m.a

The Attempt at a Solution


Since the velocity is constant, the acceleration will be 0. If that is correct the net force is going to be 0, which doesnt make any sense.
 

Answers and Replies

  • #2
gneill
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Since the velocity is constant, the acceleration will be 0. If that is correct the net force is going to be 0, which doesnt make any sense.
Why's that? Did you draw the Free Body Diagram?
 
  • #3
cnh1995
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If that is correct the net force is going to be 0, which doesnt make any sense.
The "net" force is zero. You are asked to find the force that needs to be "applied" to the box.
 
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  • #4
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The "net" force is zero. You are asked to find the force that needs to be "applied" to the box.
Is there a formula that I can use to find the "applied force"?
 
  • #5
gneill
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Is there a formula that I can use to find the "applied force"?
That's the purpose of this exercise: You're meant to find that formula by analyzing the problem using the given information.

As already mentioned, you need to draw the FBD to see how the forces combine.
 
  • #6
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That's the purpose of this exercise: You're meant to find that formula by analyzing the problem using the given information.

As already mentioned, you need to draw the FBD to see how the forces combine.
Is it going to be 4N because the forces have to be balanced?
 
  • #7
cnh1995
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Is it going to be 4N because the forces have to be balanced?
Yes.
 

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