100 likes | 262 Views
P H Y S I C S Chapter 3: Newton’s Laws of Motion Section 3A: Forces and Free-Body Diagrams. Force. Action that changes an object’s state of motion Slow down Speed up acceleration Change direction. Two Types. 1) Contact Force: through contact push/pull
E N D
P H Y S I C S Chapter 3: Newton’s Laws of Motion Section 3A: Forces and Free-Body Diagrams
Force • Action that changes an object’s state of motion • Slow down • Speed up acceleration • Change direction
Two Types 1) Contact Force:through contact • push/pull 2) Field Force:at a distance • gravity/electromagnetism
Free Body Diagram • Shows all forces (vector) acting on an object • Unit for force = N (Newton) FN = 500 N Fp= 1000 N Ff = 200 N Fg = 500 N
Newton • The amount of force it takes to accelerate a 1kg mass at 1 m/s2 • 1N = 1kg*m/s2
Common Forces • Fg = weight downward • FN = normal perpendicular to surface • Ff = friction (includes air) opposite to motion • Fp= push/pull • FT= tension in string FRICTION FN FRICTION Fg
Net Force • Vector sum of all forces on an object ΣF = (summation) net force • x and y components: F(x) = F·cosθ F(y)= F·sinθ Fp(y) Fp θ Fp(x)
In-Class Problem #1 A 9 N book sits at rest on a table. ΣF = 0 N
In-Class Problem #2 A sky diver that weighs 600 N falls towards the earth and experiences a wind resistance of 250 N. ΣF = 350 N