Force and Acceleration

Newton’s second law:  acceleration – change in velocity – ΔV  (speed or direction), a = F/m ; directly proportional to net Force in that direction, inversely proportional to mass;   mass resists acceleration (inertia)

Free fall:  (only gravity)  no air, objects in free fall have equal acceleration, 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 Σ F=0) , gravitational acceleration = 9.8 m/s²

with air (what we’re used to):  air drag (like friction) slows an object, 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)

Explain the concept of acceleration.  Why can acceleration not occur if an object is in equilibrium?  How does mass affect acceleration?

Compare and contrast speed and velocity and acceleration.

Compare and contrast free fall without air and with air.  Why do all objects fall at the same speed without air, but at very different rates in the atmosphere?  Explain terminal velocity.  What will happen to a falling body’s velocity if there is no air?