Kinetic Friction Problem [FORCES]

In summary, to find the mass of the block being pushed across a horizontal surface with a coefficient of kinetic friction of 0.15, a 150 N horizontal force is applied and the block accelerates at 2.53 m/s^2. The frictional force is found using Ff = μFN, and the normal force is found using FN = mg. Then, using the equation F=ma and substituting in the values for Fa and Ff, the mass of the block can be solved for.
  • #1
harujina
77
1

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?
 
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  • #2
harujina said:

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
Ohh ok, so I did Fa - Ff + Ff = ma + μmg
and I got the correct mass. Thank you so much!
 

What is kinetic friction?

Kinetic friction is the force that opposes the motion of an object when it is in contact with a surface and moving.

How is kinetic friction different from static friction?

Kinetic friction occurs when an object is already in motion, while static friction occurs when an object is at rest and trying to be set in motion.

What factors affect the magnitude of kinetic friction?

The magnitude of kinetic friction is affected by the type of surfaces in contact, the normal force between the surfaces, and the roughness of the surfaces.

How is kinetic friction calculated?

Kinetic friction is calculated by multiplying the coefficient of kinetic friction (μk) by the normal force (Fn): Fk = μk * Fn.

How can kinetic friction be reduced?

Kinetic friction can be reduced by using lubricants, polishing the surfaces, or by using materials with lower coefficients of friction.

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