Calculate Block Friction: 2-kg Block & Horizontal Spring

  • Thread starter anastasiaw
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In summary, the problem involves a 2-kg block resting against a compressed horizontal spring with a spring constant of 120 N/m. When released, the block slides across a table and stops 47 cm from where it was released. The goal is to calculate the coefficient of kinetic friction between the block and the table. To do so, you can use the equations W=.5kx^2 and W=Fd to find the force applied by the spring (4.136 N) and then use F=μk*F(n) to find the normal force, which is equal to the weight of the object. Finally, consider the work done by the frictional force, which can be calculated using the equation μk x Normal
  • #1
anastasiaw
17
0

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?
 
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  • #2
The table is horizontal. Consider the vertical forces acting on the block.
 
  • #3
Doc Al said:
The table is horizontal. Consider the vertical forces acting on the block.

Okay, gravity? How do I apply that to this problem?
 
  • #4
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?
 
  • #5
anastasiaw said:
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.
 
  • #6
That's it.
 
  • #7
Consider the work done by frictional force. It will be equal to?
μk x Normal Force = ?
 
  • #8
anirudh215 said:
μk x Normal Force = ?
That's the friction force. How do you find work?
 

1. What is block friction?

Block friction is the force that resists the motion of an object along a surface. It is caused by the microscopic roughness of the two surfaces in contact, which creates resistance and slows down the movement of the object.

2. How do you calculate block friction?

To calculate block friction, you need to know the coefficient of friction between the two surfaces in contact and the normal force acting on the object. The formula for block friction is F = μN, where F is the force of friction, μ is the coefficient of friction, and N is the normal force.

3. What is the coefficient of friction?

The coefficient of friction is a dimensionless constant that represents the roughness of the two surfaces in contact. It is usually denoted by the symbol μ and can range from 0 (no friction) to 1 (maximum friction).

4. How is block friction affected by the weight of the object?

The weight of the object does not directly affect block friction. However, it does affect the normal force, which is used to calculate the force of friction. The greater the weight of the object, the greater the normal force, and therefore the greater the force of friction.

5. Can block friction be reduced?

Yes, block friction can be reduced by using lubricants between the two surfaces in contact. Lubricants create a thin layer that reduces the roughness and allows the object to slide more easily. Additionally, choosing materials with lower coefficients of friction can also help reduce block friction.

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