Finding horizontal force using mass and static friction?

AI Thread Summary
To find the horizontal force necessary to move a 30 kg box with a static friction coefficient of 0.75, the correct formula is Fs = μFn, where Fn is the normal force. The normal force for a horizontal surface is equal to the weight of the box, calculated as Fn = mass × gravity (30 kg × 9.8 m/s² = 294 N). Therefore, the static friction force is Fs = 0.75 × 294 N, resulting in a required horizontal force of 220.5 N to initiate movement. The discussion emphasizes the importance of understanding the underlying principles rather than just solving for a specific problem. Mastery of these concepts is essential for tackling various physics challenges.
Infinite324
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Homework Statement


There is a box that has a mass of 30 kg. The coefficient of the static friction is 0.75. Find the horizontal force.

Homework Equations


Fs=muFn
F=ma

The Attempt at a Solution


Fs=(.75)(.98)(.30)=.2205 N

That is probably way off... I am very confused right now. Could someone please explain the steps to solving it?
 
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This can't possibly be the exact problem statement. Please provide the exact problem statement (word for word).

Chet
 
The mass of the garbage can is 30 kg. The coefficient of the static friction between the can and the ground is .75.
What is the horizontal force necessary to get the can moving?
 
Infinite324 said:
The mass of the garbage can is 30 kg. The coefficient of the static friction between the can and the ground is .75.
What is the horizontal force necessary to get the can moving?
Much better. Now in your post #1, what does the 0.98 represent, and what does the 0.30 represent (including their units)?

Chet
 
.98 m/s/s represents gravity and sorry I typed it wrong. It should be 30 N
 
30 kg not 30 N
 
Infinite324 said:
.98 m/s/s represents gravity and sorry I typed it wrong. It should be 30 N
It should be 9.8 m/s/s. How did the 30 kg become 0.30?

Chet
 
Wow yes 9.8 for Gravity. How should I continue then?
 
Infinite324 said:
Wow yes 9.8 for Gravity. How should I continue then?
According to your understanding, you tell me. You almost had it right to start with.

Chet
 
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  • #10
Should I multiply (9.8)(30)(.75)?
 
  • #11
Infinite324 said:
Should I multiply (9.8)(30)(.75)?
If you're not sure about this, you need to go back and review your text and/or notes. The objective of studying a course is so that you can understand the fundamentals (and use this to solve a wide array of problems), rather than just to solve one specific problem.

Chet
 
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