Exam Questions: Solving for Pressure, Force, and Density

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In summary: To find the area of the heel, you just need to use the formula for the area of a circle (since the heel is circular). Once you have the force and area, you can use the formula for pressure to find the answer. In summary, to find the pressure the woman exerts on the floor, use the formula for pressure (force per unit area) with the given mass and area of the heel.
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RaidersFan
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Homework Statement


a 47kg women balances on one heel of a high heeled show. if the heel has a radius of 1.4cm what pressure does she exert on the floor?










Homework Equations


rho=m
v


The Attempt at a Solution


= 47kg = 33.5
1.4cm





Homework Statement


The pascal principle is used to operate a dentists chair. assume that the pressure everywhere in the fluid is 13.5 kpa. if the small cylinder(piston) has an area of 0.007m(squared) and the large cylinder(piston) has an area of 0.08m(squared) calculate the force on each cylinder.










Homework Equations


i think the equation is f=af
a


The Attempt at a Solution


=(3.14)(0.007)squared(13.5)
0.08(squared)
=.32





Homework Statement


a gold nugget weighs 1.23N in air. when suspended from a string and submerged in water its apparent weight (T) is 1.09N. calculate the density of the gold nuggett.










Homework Equations


density=mass
volume


The Attempt at a Solution


= 1.23N
(3.14)r(squared) x h
=





Homework Statement


water enters a cylindrical pipe 3.5cm in diameter at a speed of 1.6m/s. if the pipes diameter is suddenly reduced to 2.1cm, what is the max velocity of the water moving through the smaller pipe?










Homework Equations


AV=AV


The Attempt at a Solution


3.14(3.5)(1.6)=A(2.1)





Homework Statement


air is pushed through a forced-air furnace duct at a speed of 4.7m/s. the duct is rectangular and measure 58cm by 23cm. how fast will air move through a smaller portion of the duct that is also rectangular and measures 35cm by 23cm.










Homework Equations


AV=AV


The Attempt at a Solution


3.14(58)V=23(4.7)





Homework Statement


a force of 19N[E] pushes a box of mass 13.2kg across a level floor at a constant speed. calculate the coefficient of kinetic friction (,U) between the two surfaces.










Homework Equations


,U=f
mg


The Attempt at a Solution



= 19
13.2(9.80)
= 19
129
=0.14
129








i know its a lot of work there so you can do all of them or just 1 or how every many you want to. I am just struggling on these questions and my exam is tomorrow and i really need some help so if you guys are able to help me out i would really appreciate it. thanks so much for doing this guys. :smile:
oh and u can delete my other thread since i read cristos post.
 
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  • #2
In response to your first question:

Pressure is defined as a force per unit area. You are given mass and, assuming the woman is on Earth, the force exerted by her shoe can easily be found by basic mechanics.
 
  • #3

Hello, it looks like you have a variety of questions related to pressure, force, and density. I'm happy to help you work through these problems and provide some guidance.

First, let's start with the problem about the 47kg woman balancing on one heel of a high heeled shoe. You're on the right track with using the equation density = mass/volume. However, you need to consider the units for each variable. Mass should be in kilograms (kg) and volume should be in cubic meters (m^3). So, your final answer should be in units of pressure, which is pascals (Pa). I recommend converting the radius of the heel from centimeters to meters before plugging it into the equation.

For the next problem about the Pascal principle and the dentist's chair, you're correct in using the equation F = A*P, where F is force, A is area, and P is pressure. However, you need to be careful with your units. The pressure is given in kilopascals (kPa), so you need to convert it to pascals (Pa) before using it in the equation. Also, don't forget to include the units for the area (m^2) in your calculation.

Moving on to the problem about the gold nugget, you're on the right track with using the equation density = mass/volume. However, you need to consider the units again. The weight is given in Newtons (N), so you need to convert it to kilograms (kg) before using it in the equation. Also, the volume of the gold nugget is given in terms of its dimensions (radius and height), so you'll need to use the equation for the volume of a cylinder (V = πr^2h) and plug in the given values.

For the problem about the water entering a cylindrical pipe, you're correct in using the equation AV = AV. However, you need to be careful with your units again. The velocity is given in meters per second (m/s), so you need to convert it to centimeters per second (cm/s) before using it in the equation. Also, don't forget to include the units for the areas (cm^2) in your calculation.

Moving on to the problem about air being pushed through a forced-air furnace duct, you're on the right track with using the equation AV = AV. However, you need to be careful
 

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