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Physics Mechanics- friction

Shah 72

Member
Apr 14, 2021
197
View attachment 11145
It's the 10th question. Iam getting the ans for R=90cos34= 74.6 and F=-30.3N, so I get total contact force by using the formula c= sqroot(f^2+R^2)= 80.52N
The ans in the text book is 92.2N. Iam not getting the right ans for coefficient of friction also which is 0.393
 

skeeter

Well-known member
MHB Math Helper
Mar 1, 2012
938
Attachment doesn't show ...
 

Shah 72

Member
Apr 14, 2021
197

skeeter

Well-known member
MHB Math Helper
Mar 1, 2012
938
I get $\mu = 0.393$ ...

FBD_incline.jpg
 

skeeter

Well-known member
MHB Math Helper
Mar 1, 2012
938
Can you pls show me the working
no.

I've provided the correct FBD ... this one is on you.

Hint: the system is in static equilibrium in both the parallel & perpendicular directions respective to the incline.
 

Shah 72

Member
Apr 14, 2021
197
no.

I've provided the correct FBD ... this one is on you.

Hint: the system is in static equilibrium in both the parallel & perpendicular directions respective to the incline.
R=90cos34
F=90sin34-20
Mu=0.406
I don't get the right ans
 

skeeter

Well-known member
MHB Math Helper
Mar 1, 2012
938
R is incorrect … what about the component of the 20N applied force perpendicular to the incline?

F net is incorrect … the component of the 20N applied force parallel to the incline is not 20.
 

Shah 72

Member
Apr 14, 2021
197
R is incorrect … what about the component of the 20N applied force perpendicular to the incline?

F net is incorrect … the component of the 20N applied force parallel to the incline is not 20.
R+20sin34= 90cos34
Is this the way to do?
 

Shah 72

Member
Apr 14, 2021
197
R is incorrect … what about the component of the 20N applied force perpendicular to the incline?

F net is incorrect … the component of the 20N applied force parallel to the incline is not 20.
20210514_092813.jpg
 

skeeter

Well-known member
MHB Math Helper
Mar 1, 2012
938
The problem statement says the 20N force is horizontal … that would be w/respect to the Earth’s surface, not the surface of the incline.

The reaction force in your diagram is also incorrect.

Your FBD looks nothing like the one I posted.

If you still can’t get the correct value for $\mu$, I recommend you seek assistance from your instructor.

I’m done.
 

Shah 72

Member
Apr 14, 2021
197
The problem statement says the 20N force is horizontal … that would be w/respect to the Earth’s surface, not the surface of the incline.

The reaction force in your diagram is also incorrect.

Your FBD looks nothing like the one I posted.

If you still can’t get the correct value for $\mu$, I recommend you seek assistance from your instructor.

I’m done.
Ok no problem. I will try to work it out. Thank you!
 

Shah 72

Member
Apr 14, 2021
197
The problem statement says the 20N force is horizontal … that would be w/respect to the Earth’s surface, not the surface of the incline.

The reaction force in your diagram is also incorrect.

Your FBD looks nothing like the one I posted.

If you still can’t get the correct value for $\mu$, I recommend you seek assistance from your instructor.

I’m done.
I got the ans. So F= 33.7N and R=85.8N
I got the ans 0.393.
Thank you so much!