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4.8 p. 167. Purpose: To solve word problems using uniform motion. Homework: Finish teaching worksheet. P. 169 – 170 1-11 all. Notes. Rate x Time = Distance There are 3 specific types of motion we will be covering.
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4.8 p. 167 • Purpose: To solve word problems using uniform motion. • Homework: Finish teaching worksheet. • P. 169 – 170 1-11 all.
Notes • Rate x Time = Distance • There are 3 specific types of motion we will be covering. • 1. Opposite Direction: You set up the equations as Distance 1 + Distance 2 = Total Distance
Example #1 • Mary and Michael leave school at the same time in opposite directions. Michael is walking and Mary is biking going 6 km faster. If they are 18 km apart after 1.5 h, what is the rate of each? • Set up the information in the table given to you.
Example #1 (cont.) • Rate x Time = Distance • Mary x + 6 1.5 1.5(x + 6) • Mike x 1.5 1.5 x • Distance 1 + Distance 2 = Total Distance • 1.5x + 9 + 1.5x = 18 • 3x + 9 = 18 • 3x = 9 x = 3 • Mary’s rate: 9 km Michael’s rate: 3 km
Notes • 2. Same Direction: You set up the equation as Distance 1 = Distance 2 BECAUSE they are covering the same distances. • EXAMPLE #2. • Carla begins biking south at 20 kmh at noon. Dean leaves from the same point 15 min later to catch her. If he bikes at 24 kmh, how long will Dean overtake her?
Example #2 (cont.) • Set up the info. in your chart. • Rate x Time = Distance • Carla 20 x + 15 20(x + 15) • Dean 24 x 24x • Distance 1 = Distance 2 • 20x + 300 = 24x • 300 = 4x x = 75 • It will take 75 min. or 1 ¼ hours.
Notes • 3. Round Trip: This is also set up as Distance Going = Distance Coming Back • EXAMPLE #3. • Mark drove his car to the shop at 48 kmh and walked back home at 8 kmh. The drive took him 10 min less then the walk home. How far did Mark walk and for how long? • Set up the chart.
Example #3 • Rate x Time = Distance • To 48 x – 10 48(x – 10) • From 8 x 8x • Distance To = Distance From • 48x – 480 = 8x -8x and +480 to both • 40x = 480 x = 12 • 12 min walk 1.6 km. • **You can also substitute fractions for time