Find the frictional force on the block

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Homework Help Overview

The problem involves determining the frictional force acting on a block when a horizontal force is applied, along with finding the coefficient of kinetic friction and the net force. The subject area is dynamics, specifically focusing on forces and friction in a horizontal motion context.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationships between applied force, net force, and frictional force. There are attempts to calculate the net force using F=ma and to understand the implications of kinetic friction. Questions arise regarding the definitions and relationships between frictional force and coefficient of kinetic friction.

Discussion Status

The discussion has progressed with some participants successfully calculating the net force and frictional force. Guidance has been provided to consider the problem in reverse order and to visualize the forces through free body diagrams. Multiple interpretations of the relationships between forces are being explored.

Contextual Notes

Participants are encouraged to show their reasoning and calculations as part of the learning process. There is an emphasis on understanding the definitions and relationships involved in the problem, particularly regarding kinetic friction.

katie beisel
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Homework Statement



When an 8.0 N force is exerted horizontally on a 10.0 kg block, the block’s acceleration across a level surface is 0.2 m/s2.

a. Find the coefficient of kinetic friction between the block and the surface.

b. Find the frictional force on the block.

c. Find the net force.

Homework Equations



F=ma?
Ff = mu x fN
fk = muk x fN

The Attempt at a Solution



i can't find the kinetic mu so I'm not sure how to get any of it
 
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Try answering those three questions in reverse order. First: What's the net force on the block?
 
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katie beisel said:

Homework Statement



When an 8.0 N force is exerted horizontally on a 10.0 kg block, the block’s acceleration across a level surface is 0.2 m/s2.

a. Find the coefficient of kinetic friction between the block and the surface.

b. Find the frictional force on the block.

c. Find the net force.

Homework Equations



F=ma?
Ff = mu x fN
fk = muk x fN

The Attempt at a Solution



i can't find the kinetic mu so I'm not sure how to get any of it
Hello katie beisel. Welcome to PF.

In general, you need to show effort at solving/understanding the problem before we can help you.

For your problem, it may not be best to answer the questions in order: a, b, c.

Try answering any part you can.
 
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Doc Al said:
Try answering those three questions in reverse order. First: What's the net force on the block?
ok i got that f net is 2 N by using Fnet = ma and i have that the force normal is 98 N
 
katie beisel said:
ok i got that f net is 2 N by using Fnet = ma and i have that the force normal is 98 N
Excellent! Part C is done.

Now work on B. Hint: Draw a free body diagram for the block.
 
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Doc Al said:
Excellent! Part C is done.

Now work on B. Hint: Draw a free body diagram for the block.
would the frictional force be 6 N because the force push is 8 N and the net force is 2 N so 8 - 2 = 6?
 
katie beisel said:
would the frictional force be 6 N because the force push is 8 N and the net force is 2 N so 8 - 2 = 6?
Exactly right! B is done.

Keep going.
 
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Doc Al said:
Exactly right! B is done.

Keep going.
is the frictional force and the kinetic friction the same?
 
katie beisel said:
is the frictional force and the kinetic friction the same?
Yes, since the block is sliding, the friction is kinetic friction.
 
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Doc Al said:
Yes, since the block is sliding, the friction is kinetic friction.
ok so then the coefficient of kinetic friction is .06 and with sig figs its .1
 
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katie beisel said:
ok so then the coefficient of kinetic friction is .06 and with sig figs its .1
.06 is already rounded to one sig fig. (Leading zeroes don't count.)

But good! You solved it.

Next time don't be shy about jumping in wherever you can. (And always show how you arrived at an answer.)
 
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