U3f – L4 March 29, 2011 DRILL • Solve these problems • 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? • 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 Classwork • 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 – L3 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 – L4 Classwork 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 givninformation P1 = 5psi 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 givninformation 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 givninformation 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