Finding actual static friction given mass, external force, and angle.

In summary, the actual static frictional force acting on the block is less than or equal to 25 N, with a maximum value of 0.102(25.0kg)(9.80m/s^2)=25.05 N. The actual force may be less than this maximum value if the block is not moving.
  • #1
Scarlet-
1
0
1. What is the actual static frictional force that acts on the block if an external force of 25.0 N acts horizontally on the block? ________N The mass of the block is 25.0kg. Assume g=9.80m/s^2



Homework Equations


I am using: static frictional force=(coefficient of static friction)(mass)(gravity)


The Attempt at a Solution


25N=us(25.0kg)(9.80m/s^2)
us=0.102

Of course this is obviously wrong because I am not searching for the coefficient of static friction. Would you be able to guide me to the correct equation for this type of problem?

4. Other equations I am given
T=fs, T=Mg, N=Mg


Thanks,
Scarlet-
 
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  • #2
Is the block moving when the 25 N force acts on it?
 
  • #3
Welcome to PF!

Hi Scarlet-! Welcome to PF! :smile:

(have a mu: µ and try using the X2 tag just above the Reply box :wink:)
Scarlet- said:
1. What is the actual static frictional force that acts on the block if an external force of 25.0 N acts horizontally on the block? ________N The mass of the block is 25.0kg. Assume g=9.80m/s^2

The question asks for the force, not for µ. :wink:

And remember, the actual static frictional force is less than or equal to µN.

If the block isn't moving, then the horizontal components must add to zero,

so the friction force must be … ? :smile:
 

1. What is static friction?

Static friction is the force that resists the motion of an object when it is in contact with a surface and not moving. It is caused by the interlocking of microscopic bumps and ridges on the surfaces of two objects in contact.

2. How is static friction different from kinetic friction?

Static friction only occurs when two objects are in contact and not moving, while kinetic friction occurs when there is relative motion between two objects in contact. Static friction is generally greater than kinetic friction.

3. How do you calculate the value of static friction?

The value of static friction can be calculated using the formula Fs ≤ μsN, where Fs is the force of static friction, μs is the coefficient of static friction, and N is the normal force exerted by the surface on the object.

4. What factors affect the value of static friction?

The value of static friction depends on the coefficient of static friction, the normal force, and the roughness and material of the surfaces in contact.

5. How do you find the coefficient of static friction?

The coefficient of static friction can be determined experimentally by gradually increasing the force applied to an object until it starts to move, and dividing this force by the normal force. It can also be found by using the equation μs = tanθ, where θ is the angle of inclination between the surface and the horizontal.

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