MHB Mechanics: Find Coefficient of Friction on 34° Slope w/ 0.4

Shah 72
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A particle slides up a slope at angle 34 degree to the horizontal with coefficient of friction 0.4. It passes a point P on the way up the slope with 3m/s and passes it on the way down the slope with speed 2 m/s. Find the coefficient of friction between the particle and the slope.
Coefficient of friction=0.4
F=m×a
While going up
-0.4×10cos 34-10sin 34=a
a=-8.91m/s^2.
V^2=u^2+2as
I get the eq
V^2=9-2×8.91s
I don't understand how to calculate further.
Pls help
 
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Shah 72 said:
A particle slides up a slope at angle 34 degree to the horizontal with coefficient of friction 0.4. It passes a point P on the way up the slope with 3m/s and passes it on the way down the slope with speed 2 m/s. Find the coefficient of friction between the particle and the slope.
Coefficient of friction=0.4
F=m×a
While going up
-0.4×10cos 34-10sin 34=a
a=-8.91m/s^2.
V^2=u^2+2as
I get the eq
V^2=9-2×8.91s
I don't understand how to calculate further.
Pls help

wait ... what?
 
skeeter said:
wait ... what?
I don't know how to find the coefficient of friction as if I take v^2= u^2+ 2as, there are two unknown factors which is v and s. So I don't know how to calculate.
 
Shah 72 said:
I don't know how to find the coefficient of friction as if I take v^2= u^2+ 2as, there are two unknown factors which is v and s. So I don't know how to calculate.
skeeter is pointing out that you were given the answer in the problem statement. Look at the bold sections.

-Dan
 
skeeter said:
wait ... what?
I tried but iam getting the same ans. I have no clue.
 
Shah 72 said:
I tried but iam getting the same ans. I have no clue.

Did you read the problem statement? It clearly states the coefficient of friction is 0.4 … why then are you trying to find the coefficient of friction when it’s given?
 
skeeter said:
Did you read the problem statement? It clearly states the coefficient of friction is 0.4 … why then are you trying to find the coefficient of friction when it’s given?
The question asks me to. That's why this question is so confusing. And the ans in the textbook is 0.259
 
Shah 72 said:
The question asks me to. That's why this question is so confusing. And the ans in the textbook is 0.259
Then something is wrong with the problem statement. Talk to your instructor.

-Dan
 
up the incline …

$a = -[10\sin(34)+4\cos(34)] = -8.91 \, m/s^2$

$\Delta x = \dfrac{0^2-3^2}{2a} = 0.51 \, m$

down the incline …

$a = \dfrac{2^2-0^2}{2 \Delta x} = 3.96 \, m/s^2$

$\mu = \dfrac{10\sin(34) - a}{10\cos(34)} = 0.2$

not a very well engineered problem, imo.
 
  • #10
skeeter said:
up the incline …

$a = -[10\sin(34)+4\cos(34)] = -8.91 \, m/s^2$

$\Delta x = \dfrac{0^2-3^2}{2a} = 0.51 \, m$

down the incline …

$a = \dfrac{2^2-0^2}{2 \Delta x} = 3.96 \, m/s^2$

$\mu = \dfrac{10\sin(34) - a}{10\cos(34)} = 0.2$

not a very well engineered problem, imo.
Tha
skeeter said:
up the incline …

$a = -[10\sin(34)+4\cos(34)] = -8.91 \, m/s^2$

$\Delta x = \dfrac{0^2-3^2}{2a} = 0.51 \, m$

down the incline …

$a = \dfrac{2^2-0^2}{2 \Delta x} = 3.96 \, m/s^2$

$\mu = \dfrac{10\sin(34) - a}{10\cos(34)} = 0.2$

not a very well engineered problem, imo.
Thank you very very much!
 
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