Please Grab a Chromie

Let's take a look at a couple of multiple choice problems... be prepared to present your responses to 1 - 3

General problem solving strategies for force problems:

1) Always use ALL of Newton's 3 to evaluate the problem. In particular you MUST determine whether the object is accelerating, at rest or constant velocity..... <WHY?>

2) Always use the SUM-OF-THE-FORCES versions of Newton's 2nd. Also, make sure to componentize forces in terms of horizontal or vertical motion (careful, horizontal and vertical aren't always purely x and y)

3) Make sure you have successfully identified the forces present using Newton's 3rd. Using the wolgemuthian noun-verb-noun strategy will help.

4) Introduction to system analysis (Kahn Academy does this VERY well by the way... look for "The Easy Way")

Ramps	Hangers	Elevators
Ramp Hangers	Draggers

Ramps - Find the force accelerating the block down the ramp	Hangers - Find the tension on each cable	Elevators - If the persons mass is 85 kg, what is that persons weight if the elevator accelerates upwards at 1.15 m/s/s. What is that person's weight if the elevator accelerates downward at 1.15 m/s
Ramp Hangers m1 - 75 kg m2 = 95 kg. What happens if we disregard friction and θ = 50. degrees?	Draggers - Mass of A, B & C are all 10.0 kg. Find the force F and the tension in both lines if the entire system accelerates at 3.50 m/s/s