DAY 7 I. Addition of Velocities in Two Dimensions: Relative Velocity

(see Trinklein P.44-47 & P.47 Q#1&2 & P.48 P#5,6 &7 and new Bueche xerox P.55-58 &60 and P.63 P#47,48 &49-ALL 8 QUESTIONS AND PROBLEMS BELOW)

1. Explain the statement "All motion is relative."

2.a) What is a reference object? b) When we describe motion, what is the most common reference object?

3. A motorboat heads due east at 12m/s across a river that flows toward the south with a current of 3.5m/s. a)What is the resultant velocity relative to an observer on the shore? b) If the river is 1360m wide, what is the time for the boat to cross? c)How far downstream is the boat when it reaches the other side? (O=16o,vR=13m/s,t=110s,s=380m)

4. Find the air velocity of a plane that must have a relative ground velocity of 250.0km/h north if it encounters a wind pushing it toward the northeast at 75.0 km/h? (vP =204km/h,O=15.1o W of N)

5. A swimmer can swim in still water at a speed of 9.50m/s. He intends to swim directly across a river that has a downstream current of 3.75m/s. a) What heading must he take? b) What is his velocity relative to the riverbank? (O =23.3o, vg =8.71m/s)

6. A helicopter is headed(pointed in the direction of)due north. It can fly 75mi/h in still air, and the wind is coming from the northeast at 20mi/h. What is the helicopter’s velocity relative to the ground? How far does the helicopter travel in 20min?

7. You want to paddle your kayak directly across a river, whose current flows at 0.85m/s. You are capable of paddling at a speed of 2.1m/s. a) In which direction must you head your boat in order to move directly across the river? b) If the river is 45m wide, what times does it take you to cross?

8. An airplane has an airspeed(in still air) of 650km/h. The plane is heading 25o west of north, but the pilot notices that the plane is actually traveling 18o west of north. What eastward wind velocity is the plane encountering?

II. Assignment : COMPLETE Study Sheet 2; STUDY UNIT 2 SKILLS &Ch.3 P.64 Goals