Frictional force, normal force and coefficient of friction

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SUMMARY

The discussion focuses on calculating the frictional force (Ff), normal force (Fn), and coefficient of friction (u) for a 0.2kg object on a 35-degree incline. The normal force was calculated as Fn = 1.61 N using the formula Fn = m x a x cos(θ), where m is mass and θ is the angle of incline. Since the block is not accelerating, the net force is zero, indicating that the component of gravitational force parallel to the incline equals the frictional force. The discussion emphasizes the importance of drawing a diagram to visualize the forces acting on the object.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with trigonometric functions, particularly cosine
  • Knowledge of basic physics concepts such as friction and forces
  • Ability to perform vector resolution of forces
NEXT STEPS
  • Learn how to calculate the coefficient of friction using Ff and Fn
  • Study the concept of static vs. kinetic friction
  • Explore the effects of different angles on frictional forces
  • Investigate the role of mass in frictional force calculations
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Students studying physics, particularly those focusing on mechanics and forces, as well as educators seeking to explain the concepts of friction and inclined planes.

lisa1991
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Homework Statement



Calculate the frictional force, normal force and coefficient of friction for an 0.2kg object that is lying on a 35 degree incline.


Homework Equations



Ff= u x Fn
F= m x a

The Attempt at a Solution



I managed to get FN= m x a x cos# = -9.81 x 0.2 x cos35 = 1.61 N

I have no idea how to get Ff, but when I work that out I will be able to work out coefficient (u). Thanks for any help
 
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Since the block is not accelerating, the net force must be zero. Look at all the forces, and find their components along the incline and normal to it.
 
sorry also should have mentioned that 35 degrees is the angle the object starts to move down the slope
 
lisa1991 said:
sorry also should have mentioned that 35 degrees is the angle the object starts to move down the slope

Hi lisa1991! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

At 35° the component of gravity overcomes friction, so the forces are equal and opposite. Draw a diagram showing the incline and the direction of the forces involved.
 
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The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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