# CH04. Problems ```CH04. Problems
Relative Motion
Textbook (9th Ed, CH04, P.75)
••75 A train travels due south at 30 m/s
(relative to the ground) in a rain that is blown
toward the south by the wind. The path of
each raindrop makes an angle of 70&deg; with the
vertical, as measured by an observer stationary
on the ground. An observer on the train,
however, sees the drops fall perfectly vertically.
Determine the speed of the raindrops relative
to the ground.
Textbook (9th Ed, CH04, P.76)
••76 A light plane attains an airspeed of 500 km/h. The pilot sets
out for a destination 800 km due north but discovers that the
plane must be headed 20.0&deg; east of due north to fly there
directly. The plane arrives in 2.00 h.
What were the (a) magnitude and (b) direction of the wind
velocity?
Textbook: p82; …
Old way: not easy to solve
New way: think of water motion as an added/subtracted distance
Textbook Summary
Acceleration changes direction where
The two components changes but the
Magnitude stays constant.
The y component is positive in the
Lower half. Maximum at bottom
Point A
Textbook
summary
```