Efficiently Solving a Simple Pulley Question with Mass and Force Calculations

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To raise herself slowly at constant speed using the bucket-pulley system, the window washer must consider the forces acting on the bucket. The total mass of the person and bucket is 66.3 kg, leading to a gravitational force of approximately 650 N. The key to solving the problem lies in understanding the tension in the rope, which is equal to the weight when there is no acceleration. The pulley arrangement involves two parallel strings, with the washer pulling down on one side to lift herself and the bucket. Properly analyzing the tension will lead to the correct force needed for her upward movement.
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Homework Statement


A window washer pulls herself upward using the bucket-pulley apparatus shown in figure below.


Homework Equations


With what force must she pull downward to raise herself slowly at constant speed? The mass of person plus bucket is 66.3 kg.


The Attempt at a Solution


f=ma
f=66.3 x 9.8
f=650N
wrong?
 
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I_LuV_FiZiX said:

Homework Statement


A window washer pulls herself upward using the bucket-pulley apparatus shown in figure below.


Homework Equations


With what force must she pull downward to raise herself slowly at constant speed? The mass of person plus bucket is 66.3 kg.


The Attempt at a Solution


f=ma
f=66.3 x 9.8
f=650N
wrong?

Hi I_LuV_FiZiX! :smile:

(You haven't told us what the pulley arrangement is. :rolleyes:)

Hint: in these questions, always ask yourself what the tension in the rope is. :wink:
 
the pulley arrangement is two strings parallel to each other with a pulley at the top, she is in the bucket attached to the string on the left, and she is pulling down on the pulley on the right in order to bring her and the bucket up...thanks for considering my question :smile:
 
I_LuV_FiZiX said:
the pulley arrangement is two strings parallel to each other with a pulley at the top, she is in the bucket attached to the string on the left, and she is pulling down on the pulley on the right in order to bring her and the bucket up

ok … then consider the forces on the bucket … what is the tension in the rope if there is no acceleration? :smile:
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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