What Is the Coefficient of Kinetic Friction in Brenda's Wallpaper Project?

AI Thread Summary
Brenda's wallpaper project involves calculating the coefficient of kinetic friction while using a sanding block that weighs 2.0N, pushed with a force of 3.0N at a 30-degree angle. The free body diagram indicates that the normal force acts horizontally, not vertically, which is crucial for accurate calculations. The initial calculation of the y-component of the pushing force yielded 2.6N, leading to a coefficient of kinetic friction of 1.30, which seems excessively high. Clarification is sought on the correct interpretation of forces, particularly the direction of the normal force. Accurate representation and understanding of forces are essential for solving the problem correctly.
sunfire249
Messages
2
Reaction score
0

Homework Statement


Before hanging new William Morris wallpaper in her bedroom, Brenda sanded the walls lightly to smooth out some irregularities on the surface. The sanding block weighs 2.0N and Brenda pushes on it with a force of 3.0N at an angle of 30.0 degrees with respect to the vertical, and angled toward the wall. Draw a free body diagram for the sanding block as it moves straight up the wall at a constant speed. What is the coefficient of kinetic friction between the wall and the block?

Fn = 2.0N
Theta = 30.0
Fhand = 3.0N


Homework Equations


F = UkN
y-component = ycos(theta)


The Attempt at a Solution


I drew an FBD of a block on a vertical wall with Fn pointing in the downwards direction. I extended the top part of the block a little with a dotted line to show the continuation of the y-axis, and drew a line that represented the magnitude of the hand pushing at 30degrees.

My first attempt I tried 3.0cos(30.0) (because I reasoned that if you find the y-component to the force of the hand you would find the F needed for the equation F = UkN)
I got 2.6N from this, and reworked F = UkN so it would be Uk = F/N
I plugged in Uk = 2.6N/2.0N (Normal force of the block), and got 1.30 as an answer.

This answer seems a little large to me though, considering it's the coefficient of Static Friction. So I'm just wondering where I might have gone wrong?
 
Physics news on Phys.org
The wall is vertical so the normal force is horizontal and not equal to the weight of the block, which points downward.

A good drawing always helps. Can you show yours?

ehild
 

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 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
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

A question about contact forces and friction
Replies
6
Views
5K
Contact force of block on a wall
Replies
5
Views
3K
Find the frictional force between a block and a wall
Replies
5
Views
3K
Why is the tension force equal to friction force
Replies
9
Views
7K
Coefficient of Friction when Normal Force is Reduced [HS]
Replies
5
Views
2K
Coefficient of kinetic friction?
Replies
21
Views
2K
Frictional forces and the angle for minimum frictional force
Replies
7
Views
3K
Applications of Newton's laws (friction related)
Replies
8
Views
2K
Finding Force by using the coefficient of friction and mass
Replies
16
Views
3K
Find the frictional force on the block
Replies
10
Views
2K

Hot Threads

Recent Insights

Back
Top