Lecture 8 ACT1b Gravity and Normal Forces a woman in an elevator is accelerating upwards The normal force exerted by the elevator on the woman is A) greater than B)the same as C)less than the force the woman exerts on the elevator Physics 121: Lecture 8, Pg 6
Physics 121: Lecture 8, Pg 6 Lecture 8, ACT 1b Gravity and Normal Forces A woman in an elevator is accelerating upwards The normal force exerted by the elevator on the woman is, A) greater than B) the same as C) less than the force the woman exerts on the elevator
The Free Body Diagram Newton's 2nd Law says that for an object F= ma Key phrase here is for an object. So before we can apply F= ma to any given object we isolate the forces acting on this object Physics 121: Lecture 8, Pg 7
Physics 121: Lecture 8, Pg 7 The Free Body Diagram Newton’s 2nd Law says that for an object F = ma. Key phrase here is for an object. So before we can apply F = ma to any given object we isolate the forces acting on this object:
The Free Body Diagram ■■ Consider the following case What are the forces acting on the plank? plal ank F= floor W= wall WP E earth PF PE EP EP Physics 121: Lecture 8, Pg 8
Physics 121: Lecture 8, Pg 8 The Free Body Diagram... Consider the following case What are the forces acting on the plank ? P = plank F = floor W = wall E = earth FW,P FP,W FP,F FP,E FF,P FE,P
The Free Body Diagram ■■ Consider the following case What are the forces acting on the plank? Isolate the plank from the rest of the world WP PF P/E Physics 121: Lecture 8, Pg 9
Physics 121: Lecture 8, Pg 9 The Free Body Diagram... Consider the following case What are the forces acting on the plank ? Isolate the plank from the rest of the world. FW,P FP,W FP,F FP,E FF,P FE,P
The Free Body Diagram ■■ The forces acting on the plank should reveal themselves PW PE Physics 121: Lecture 8, Pg 10
Physics 121: Lecture 8, Pg 10 The Free Body Diagram... The forces acting on the plank should reveal themselves... FP,W FP,F FP,E