Frictional Force of a Crate of Potatoes: 13 kg, 40° incline

In summary, to find the frictional force on a crate at rest on a ramp with an angle of incline of 40°, you can use the equation Ff=μmgcosα, where μ is the coefficient of friction, m is the mass of the crate, g is the acceleration due to gravity, and α is the angle of the incline. However, it is important to take into account that the static friction may not be equal to its maximum possible value and to consider the forces acting on the crate, including the weight, friction, and normal force. By using the equation ΣF = 0 and considering force components parallel to the incline, you can accurately calculate the frictional force on the crate.
  • #1
lalahelp
75
0

Homework Statement


A crate of potatoes of mass 13.0 kg is on a ramp with angle of incline 40° to the horizontal. The coefficients of friction are μs = 0.78 and μk = 0.43. Find the frictional force (magnitude) on the crate if the crate is at rest.



Homework Equations


F=ma
Ff=μmgcosα


The Attempt at a Solution



Ff=.78*13*9.81*cos40
=76.2 N


Why is my answer wrong?
 
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  • #2
You assumed that the static friction would be equal to its maximum possible value (μN). Instead, solve for the value of static friction considering that the crate is in equilibrium.
 
  • #3
What equation would I use to do that?
 
  • #4
lalahelp said:
what equation would i use to do that?
The net force is zero.
 
  • #5
I don't understand it still
 
  • #6
lalahelp said:
I don't understand it still
What forces act on the crate?
 
  • #7
the mass and friction
 
  • #8
lalahelp said:
the mass and friction
The weight, the friction, and the normal force. What direction does each act?
 
  • #9
the weights acts straight down, friction to the right, and normal force up
 
  • #10
lalahelp said:
the weights acts straight down, friction to the right, and normal force up
Consider force components parallel to the incline and apply ΣF = 0.
 
  • #11
Ok thank you I got it !
 

Related to Frictional Force of a Crate of Potatoes: 13 kg, 40° incline

1. What is the definition of frictional force?

Frictional force is the force that opposes the motion of an object when it is in contact with another object or surface.

2. How is frictional force calculated?

Frictional force is calculated by multiplying the coefficient of friction (a measure of how easily two surfaces slide against each other) by the normal force (the force exerted by the surface on the object).

3. What factors affect the frictional force of a crate of potatoes?

The frictional force of a crate of potatoes can be affected by the weight of the crate, the surface it is on, and the angle of incline.

4. How do you calculate the weight of the crate of potatoes?

The weight of the crate of potatoes can be calculated by multiplying the mass of the potatoes (13 kg) by the gravitational acceleration (9.8 m/s²), giving a weight of 127.4 N.

5. How can the frictional force of a crate of potatoes be reduced?

The frictional force of a crate of potatoes can be reduced by using a smoother surface or by decreasing the angle of incline. Additionally, using lubricants or reducing the weight of the crate can also decrease frictional force.

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