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Kinetic Friction Problem [FORCES]

  • Thread starter harujina
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  • #1
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Homework Statement



A block is pushed across a horizontal surface with a coefficient of kinetic friction of 0.15 by applying a 150 N horizontal force. The block accelerates at 2.53 m/s^2. Find the mass of the block.

Homework Equations



ƩF = ma

The Attempt at a Solution



μk = 0.15
Fa (applied force) = 150 N
a = 2.53 m/s^2
m = ?

I understand I must find the frictional force first, correct?
and Ff (frictional force) = μFN (normal force)

And to find normal force, FN = mg
but then I come across this, which also requires for me to find mass...?
What can I do?
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
26,258
618

Homework Statement



A block is pushed across a horizontal surface with a coefficient of kinetic friction of 0.15 by applying a 150 N horizontal force. The block accelerates at 2.53 m/s^2. Find the mass of the block.

Homework Equations



ƩF = ma

The Attempt at a Solution



μk = 0.15
Fa (applied force) = 150 N
a = 2.53 m/s^2
m = ?

I understand I must find the frictional force first, correct?
and Ff (frictional force) = μFN (normal force)

And to find normal force, FN = mg
but then I come across this, which also requires for me to find mass...?
What can I do?
No, you don't need to find the mass first. Just leave Ff=μmg. The total force is F is Fa-Ff. Since F=ma, Fa-Ff=ma. Put it all together and you should be able to solve for m in the end.
 
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  • #3
77
1
Ohh ok, so I did Fa - Ff + Ff = ma + μmg
and I got the correct mass. Thank you so much!
 

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