III. Force and Acceleration

1. acceleration – change in velocity – ΔV (speed or direction) in a unit of time
   
2. The acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object.
3. a = F/m
1. directly proportional to net Force in that direction
2. inversely proportional to mass
3. mass resists acceleration (inertia)

1. no air (free fall)
   
1. objects in free fall have equal acceleration
2. A = F/m = weight/m (in free fall, weight is the only force, there is no upward force. Not in equilibrium so don’t have ΣF=0)
3. A = g gravitational acceleration = 9.8 m/s²
2. with air (what we’re used to)
1. air drag (like friction) slows an object (premise behind parachutes)
2. A= F/m as above, but now there are two forces weight going down and air drag going up
• overall F is smaller (weight – drag)
• as speed increases, drag increases
• eventually ΣF=0 (not stop! just constant velocity – terminal velocity)