Calculate Block Friction: 2-kg Block & Horizontal Spring

[anastasiaw]

Homework Statement

A 2- kg block rests against one end of a horizontal spring which is compressed by 18 cm. When the spring is released, the spring forces the block to slide across a table top. It stops 47 cm from where you released it. The spring constant k is equal to 120 N/m. Calculate the constant of kinetic friction μk between the block and the table.

Homework Equations

W=.5kx^2
W=Fd

The Attempt at a Solution

I used the two equation above to find that F=4.136N

Somebody suggested I should put this into the equation F=μk*F(n), but I don't know how to find F(n). Any help?

 

[Doc Al]

The table is horizontal. Consider the vertical forces acting on the block.

 

[anastasiaw]

The table is horizontal. Consider the vertical forces acting on the block.

Okay, gravity? How do I apply that to this problem?

 

[Doc Al]

Gravity is one of the forces on the block.

Answer this: A block sits on the table. What normal force must the table exert on the block?

 

[anastasiaw]

Okay, gravity? How do I apply that to this problem?

Okay I got it -- F(n) is the normal force... the weight of the object. Thanks.

 

[Doc Al]

That's it.

 

[WiFO215]

Consider the work done by frictional force. It will be equal to?
μk x Normal Force = ?

 

[Doc Al]

μk x Normal Force = ?

That's the friction force. How do you find work?