100 likes | 441 Views
Apparent Weight. General Physics. Apparent Weight. Definition: The force exerted by the scale (F N ) Free-body Diagram: Equations: F net = F N + F g ( free-body diagram) F net =ma (Newton’s 2 nd Law) So, ma = F N + F g F g = mg (weight). F N. F g.
E N D
Apparent Weight General Physics
Apparent Weight • Definition: The force exerted by the scale (FN) • Free-body Diagram: • Equations: • Fnet=FN + Fg ( free-body diagram) • Fnet=ma (Newton’s 2nd Law) • So, ma = FN + Fg • Fg = mg (weight) FN Fg
Problem: Your mass is 60 kg. You stand on a bathroom scale in an elevator. What will the scale read if you are …..at rest Fg -= mg = (60kg)(-9.8 m/s2) = -588 N FN = 588 N FN Fg
accelerating upward at 3.0 m/s2? a Fnet FN Fg = -588 N Fnet= ma= (60kg)(3.0 m/s2) = 180N Fnet=FN +Fg , so FN =Fnet – Fg = 180N – (-588N) = 768 N Fg
moving at a constant velocity? Fnet= 0 Fg = -588 N FN = 588 N FN Fg
accelerating downward at 3.0 m/s2? Fg = -588 N Fnet= ma= (60kg)(-3.0 m/s2) = -180N Fnet=FN +Fg , so FN =Fnet – Fg = -180N – (-588N) = 408 N a Fnet FN Fg
freefalling because cable breaks? FN = 0 Weightlessness Fg