Try this at Home

You can do this with a ping pong ball and a hair dryer


St. Mary's U. Astronomy and Physics Dept.



When a fluid, moves in a single direction, it exerts very little pressure perpendicular to the direction of its flow.
The external air pressure keeps the ball in place.







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Quick Resultants Review

Same direction - ADD

Opp. Direction - Subtract

90 degrees - Pyth.




A. Resultants - Angle ≠ 90°


Find Fy and Fx of resultant

Find Fy and Fx of resultant


Fx = 4N - 3N = 1N

Fy = 3N - 1N = 2N




Ex) 5 N North & 3 N 30° S of E act concurrently (on a single point).


Find the Fx and Fy
of resultant in terms of theta

1. Sketch Vectors








1. Combine Fx and Fy 

ΣFx = 0 + 3Ncos30


ΣFx = 2.6 N


ΣFy = 5N - 3 Nsin30


ΣFy = 3.5 N

Pyth. Theorem and Tangent

R = 4.5 N 53° N of E


E = 4.5 N 53° S of W





Ranking Task

Rank the resultants from SMALLEST to LARGEST


Jan 2006








Monster Shoot Out Game

St. Mary H.S. Physics



AP Question

Hewitt Question


Ex) Relative to the ground, an airplane gains speed when it encounters wind from behind, and loses speed when it encounters wind head on.


When it encounters wind at a right angle to the direction it is pointing, its speed relative to the ground below

A. increases. 

B. decreases. 

C. is the same as if there were no wind.

D. Need more information.











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