D = rt
Uniform Motion
Three types of problems:
- Motion in opposite direction
- Motion in same direction
- Round Trip
Motion in opposite direction
For this we used different students bicycling ... Jake and Jordan in 6th period and Henri and Andy from 7th period.
Last year's examples follow:
They start at noon ;60 km apart riding toward each other. They meet at 1:30 PM. If Jake's speed is 4 km/h faster than Jordan's ( Henri is greater by the same from Andy's rate) What are their speeds?
The chart below was take from last year's examples
We set up a chart
Motion in Same Direction
Next we had a fictitious story about Ritika's Helicopter and Maya's plane ( or Ryan's helicopter and Allison's Smiling Plane) taking off from Camarillo Airport flying north. The helicopter flies at a speed of 180 mi/hr. 20 minutes later the plane takes off in the same direction going 330 mi/hr. How long will it take Maya (or Allison) to over take Ritika's ( or Ryan's) helicopter?
Let t = plane's flying time
Make sure to convert the 20 minutes ---> 1/3 hours.
We set up a chart .. Here is the chart with last year's names:
When the plane over takes the helicopter they have traveled the exact same distance so set them equal
180(t + 1/3) = 330t
180 t + 60 = 330t
60 = 150t
t = 2/5
which means 2/5 hour. or 24 minutes.
Round Trip
A ski lift carries Jenna ( or Brendan) up the slope at 6 km/h Jenna or Brendan snowboard down 34 km/h. The round trip takes 30 minutes.
Did you see the picture?
Let t = time down
then set up a chart
6(.5 -t) = 34 t
3 - 6t = 34 t
3/40 = t
Now, what's that?
0.75 hr or 4.5 minutes
How far did they snowboard... plug it in
34(0.075) = 2.55 km
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