Find Frictional force on a block

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SUMMARY

The frictional force on a block of mass 9 kg resting on a plane inclined at 30° with a static coefficient of friction of 0.7 is calculated using the equations Ff = ma and F = μ * Fn. The normal force (Fn) is determined by the gravitational force acting on the block, which is G = mg, where g = -9.81 m/s². The correct frictional force is 30.87 N, derived from the static friction formula.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Knowledge of static friction and coefficients
  • Ability to calculate normal force on an inclined plane
  • Familiarity with basic physics equations related to force
NEXT STEPS
  • Learn how to calculate normal force on inclined planes
  • Study the concept of static vs. kinetic friction
  • Explore advanced applications of friction in physics problems
  • Investigate the effects of different angles on frictional force
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and forces, as well as educators seeking to enhance their teaching of friction and inclined planes.

trivk96
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Homework Statement



A block of mass 9 kg rests on a plane inclined
at an angle of 30◦. The static coefficient of
friction between the block and the plane is
0.7.
What is the frictional force on the block?
1. 9.36841 N
2. 76.3834 N
3. 53.4684 N
4. 44.1 N
5. 30.87


Homework Equations


Ff=ma
F=μ*Fn


The Attempt at a Solution


I have no idea
 
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The point here is that FN= |G| , they have the same numerical value (are equally large), but they go in the oppposite directions , thus one is positive, the other is negative, + or - sign.

Since gravity pulls downwards, G, the gravitational force points downwards, N is the normal force (in the opposite direction).If we choose positive direction upwards, gravitational pull is negative. with g=-9,81 m/s^2. Remember G=mg, using that FN= |G| will give you the normal force and you can calculate the frictional force from your information.

trivk96 said:

Homework Statement



A block of mass 9 kg rests on a plane inclined
at an angle of 30◦. The static coefficient of
friction between the block and the plane is
0.7.
What is the frictional force on the block?
1. 9.36841 N
2. 76.3834 N
3. 53.4684 N
4. 44.1 N
5. 30.87


Homework Equations


Ff=ma
F=μ*Fn


The Attempt at a Solution


I have no idea
 

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