March 29, 2011
DRILL
Solve these problems
1. A gas is compressed from a volume of 100 mL
to a volume of 50 mL. The ending pressure is
2 psi. What was the starting pressure?
2. A 165 lb teacher stands exerts a pressure of 10
psi on a block of wood. What is the area of the
block of wood?
Take out handout from yesterday.
U3f – L4
Drill # 1
A gas is compressed from a volume of 100 mL to a
volume of 50 mL. The ending pressure is 2 psi.
What was the starting pressure?
Step 1: Write given information
P1 = ?
V1 = 100 mL
P2 = 2 psi
V2 = 50 mL
Step 2: Write the formula and solve
P1*V1=P2*V2
P1* 100 mL = 2 psi*50mL
P1*100mL = 100mL*psi
P1 =100 psi*mL/(100mL)
P1= 1psi
U3f – L4
Drill #2
A 165 lb teacher stands exerts a pressure of 10 psi
on a block of wood. What is the area of the
block of wood?
Step 1: Write given information
P = 10 psi
F = 165 lb
A =?
Step 2: Write the formula and solve
P = F/A
10psi = 165lb/A
10psi * A = 165 lb
A = 165 lb/(10 psi)
A = 16.5 in2
U3f – L4
Read these articles
Self-Cleaning Windows on page 59
Gas-Plasma Displays on page 245
Synthetic Fuels on page 265
Wind Tunnels on page 660.
For each question, letter responses in complete sentences
to the following questions?
•
•
•
•
What is this technology used for?
How does it relate to fluid technology?
What other core technologies are important for this technology?
What did people use before this technology?
U3f – L4
Equations you must know
P=F/A
(Pressure = Force / Area)
PV = k
(Pressure x Volume = Constant)
P1V1 = P2V2
(Initial P x Initial V = Final P x Final V)
U3f – L3
Work in pairs.
Solve the problem by showing
all of the steps
U3f – L4
Problem 1
A basketball has 5 psi of pressure and 100 mL of
volume. What is the pressure multiplied by the
volume equal to? If we decrease the volume to
20 mL, what is Pressure times Volume?
Step 1: Write givn information
P1 = 5 psi
V1 = 100mL
P2 = ?
V2 = 20mL
Step 2: Write the formula and solve
PV = k
5 psi * 100 mL = k
k = 500 mL*psi
U3f – L4
Problem 2
Two 175 lb teachers stand on a block of wood with
50 in2 in area. What is the total pressure
Step 1: Write given information
P =?
F = 175 lb x 2 = 350 lbs
A = 50 in2
Step 2: Write the formula and solve
P = F/A
P = 350lb/ 50 in2
P= 7 psi
U3f – L4
Problem 3
Your lungs have a volume 4000 mL when you
breathe in and 1000 mL after you exhale. If the
pressure when you breathe in is 15 psi, what is
the pressure when you breathe out
Step 1: Write givn information
P1 = 15 psi
V1 = 4000 mL
P2 = ???
V2 = 1000 mL
Step 2: Write the formula and solve
P1V1 =P2V2
15 psi * 4000 mL = P2*1000 psi
60,000 mL*psi = P2 *1000psi
P2 = 60 psi
U3f – L4
Problem 4
The air in your tires has a pressure of 50 psi and a
volume of 1,600 mL. If the pressure inside the
tire decrease to 40 psi, what would the new
volume be?
Step 1: Write givn information
P1 = 50 psi
V1 = 1600 mL
P2 = 40 psi
V2 = ??
Step 2: Write the formula and solve
P1V1 =P2V2
50 psi * 1600 mL = P2*V2
80,000 mL*psi = 40 psi *P2
P2 = 2000 mL
U3f – L4