Aside In this example the plank is not moving And it is not accelerating! So FNET ma becomes FNET =0 PW For+ FDE=O PWP F P E F PE This is the basic idea behind statics Physics 121: Lecture 8, Pg 11
Physics 121: Lecture 8, Pg 11 Aside... In this example the plank is not moving... And it is not accelerating! So FNET = ma becomes FNET = 0 This is the basic idea behind statics. FP,W + FP,F + FP,E = 0 FP,W FP,F FP,E
Example Example of a dynamics problem a box of mass m= 2kg slides on a horizontal frictionless floor. A force Fx 10N pushes on it in the i direction. What is the acceleration of the box? F=F i a m Physics 121: Lecture 8, Pg 12
Physics 121: Lecture 8, Pg 12 Example Example of a dynamics problem: A box of mass m = 2kg slides on a horizontal frictionless floor. A force Fx = 10N pushes on it in the i direction. What is the acceleration of the box? F = Fx i a = ? m j i
Example 圆■ Draw a picture showing all of the forces BF F BE FB EB Physics 121: Lecture 8, Pg 13
Physics 121: Lecture 8, Pg 13 Example... Draw a picture showing all of the forces F FB,F FF,B FB,E FE,B j i
Example 圆■ Draw a picture showing all of the forces Isolate the forces acting on the block F FB BE mg EB Physics 121: Lecture 8, Pg 14
Physics 121: Lecture 8, Pg 14 Example... Draw a picture showing all of the forces. Isolate the forces acting on the block. F FB,F FF,B FB,E = mg FE,B j i
Example 圆■ Draw a picture showing all of the forces Isolate the forces acting on the block Draw a free body diagram BF F mg Physics 121: Lecture 8, Pg 15
Physics 121: Lecture 8, Pg 15 Example... Draw a picture showing all of the forces. Isolate the forces acting on the block. Draw a free body diagram. F FB,F mg j i