Solving Friction Homework: F=ma, Fk=u*Fn

Just remember to double check the direction of your components and make sure they match the coordinate system you are using. Keep up the good work.In summary, the conversation discusses the process of analyzing forces and applying Newton's second law to solve a physics problem involving a figure and various forces acting on it. The participants also discuss potential mistakes and provide guidance on how to avoid them. Overall, the conversation demonstrates the importance of careful analysis and double-checking in solving physics problems.
  • #1
Sarah00
64
1

Homework Statement


screenshot_25.png


Homework Equations


F = ma
Fk= u * Fn

The Attempt at a Solution


By analyzing the forces into components and applying Newton's second law

Fnet on y-axis = 0
So, Fn = mg + F2sin37 - F1sin 37 = 20 + 9 = 29 N

on x-axis
F = ma
F1 cos 37 + F2 cos 37 - Ffr = ma
F1 cos 37 + F2 cos 37 - uK * Fn = ma
5*0.8 + 20*0.8 - 0.2*29 = 2a
4 + 16 - 5.8 = 2a
14.2 = 2a
a = 7.1 m/s2Can you guide me to know my mistake, please?

Thanks in adavance
 
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  • #2
Looks like you assumed the figure depicts a side view. Maybe it's an overhead view. If so, I think you should get one of the answers listed.
 
  • #3
So I find the resultant force which is:
25*0.8 - 15*0.6 = 20 i - 9j
Magnitude = 21.9 ~= 22 N

Friction force is 0.2 * 20 = 4 N

Net force = 22 - 4 = 18 N

F = ma
18 = 2a
a = 9 m/s2

thanks!
 
  • #4
Looks good!
 

FAQ: Solving Friction Homework: F=ma, Fk=u*Fn

1. What is the formula for solving friction?

The formula for solving friction is F = ma, where F represents the force of friction, m represents the mass of the object, and a represents the acceleration.

2. What does Fk stand for in the equation?

Fk stands for the force of kinetic friction, which is the resistance force that opposes the motion of an object when it is already in motion.

3. What does u*Fn represent in the equation?

u represents the coefficient of friction, which is a measure of the roughness or smoothness of the surface. Fn represents the normal force, which is the force exerted by a surface on an object that is in contact with it. Together, u*Fn represents the maximum force of static friction, which is the force that must be overcome to set an object in motion.

4. How do you calculate the coefficient of friction?

The coefficient of friction can be calculated by dividing the force of friction (F) by the normal force (Fn): u = F/Fn. It can also be determined experimentally by measuring the force required to move an object and dividing it by the normal force.

5. What are the units for the variables in the equation?

The units for the force of friction (F) and the force of kinetic friction (Fk) are typically measured in Newtons (N). The mass (m) is measured in kilograms (kg) and the acceleration (a) is measured in meters per second squared (m/s^2). The coefficient of friction (u) and the normal force (Fn) do not have specific units, but their values are typically given in decimal form.

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