Friction and the Coefficents of Friction question

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To calculate the coefficient of static friction for a 35 kg box requiring a 110 N force to start moving, the equation Ff = uFn is applied, where Ff is the frictional force and Fn is the normal force. The normal force equals the gravitational force on the box, which is 35 kg multiplied by the acceleration due to gravity (approximately 9.81 m/s²). The coefficient of static friction (u) can be found by rearranging the equation to u = Ff / Fn. Additionally, a problem involving three blocks connected by strings over a frictionless pulley is introduced, with a coefficient of friction of 0.2, requiring further calculations for tension and movement time. Understanding these concepts is essential for solving friction-related physics problems.
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Homework Statement


so my question is; A horizontal force of 110 N (forward) is required to get a 35 kg box to start moving across a floor, Calculate the coefficent of static friction.
The equations i have been given are Ff=uFn
But I have just started this unit and am so confused. I don't even know where to start.


Homework Equations





The Attempt at a Solution

 
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First, draw a free body diagram for the box - include all forces.
It may help to list what you know and what need to find (organize the info outside of the question).
 
Floor is horizantal so normal force equals gravitational force. To break frictional force, applied force must equal it.
 
1. Three blocks are tied to each other with
two pieces of string, one of which
passes over a frictionless pulley, as
shown. The coefficient of friction
between each block and the surface on
which it slides is 0.2. Just as the
system starts to move, the 3 kg and
6 kg blocks are each one metre away
from the pulley.

1.1Determine the tension in each of the strings.
1.2 How long before one of the blocks jams the pulley?
 

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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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