Coefficient of static friction and minimum horizontal force

AI Thread Summary
To determine the minimum horizontal force required to hold a 5.0 kg mass against a wall with a coefficient of static friction of 0.85, the frictional force (Ff) must equal the weight of the mass. The weight is calculated as 49 N (5.0 kg multiplied by the acceleration due to gravity). The frictional force is then calculated using the equation Ff = UFn, resulting in Ff = 0.85 * Fn. The confusion arises because the teacher's answer of 58 N suggests a different interpretation of the normal force (Fn). Ultimately, understanding that the frictional force must counteract the weight is key to solving the problem.
kamalpreet122
Messages
13
Reaction score
0

Homework Statement



A 5.0 kg mass is held against a wall with which it has a coefficient of static friction of 0.85. What is the minimum horizontal force required to hold the mass against the wall ?

The teacher said answer is 58 N .. i can't get to that answer..

Homework Equations



Ff = UFn

The Attempt at a Solution



Ff = 0.85(49)
Ff = 41.65

this answer makes sense but for some reason ..the teacher has given us a different answer :S
 
Physics news on Phys.org


Fnis the unknown.

Ff must be equal to the weight.
 


yea that makes a lot of sense thanxx a lot :D
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Coefficient of Friction when Normal Force is Reduced [HS]
Replies
5
Views
2K
Friction Forces on 2WD vs 4WD Vehicles
Replies
6
Views
1K
How Do I Determine Force of Static Friction on a Rolling Car
Replies
15
Views
2K
How do i find the coefficient of static friction?
Replies
2
Views
2K
Force of the wall against the ladder is from static friction?
Replies
6
Views
3K
Acceleration of object with friction: Homework help
Replies
1
Views
2K
Normal force at the base of a ladder
Replies
20
Views
2K
Static friction coefficient for a crate in the back of a truck
Replies
6
Views
2K
Newton's law problem: Pushing 2 stacked blocks on a horizontal table
Replies
13
Views
3K
The minimum applied force before an object slips off wall
Replies
4
Views
3K

Hot Threads

Recent Insights

Back
Top