54 Chapt. 5 Newton’s Laws and Dynamics I the positive x direction which is down the slope? What is the expression for the position x of the object as a function of time t when it starts from rest at t = 0 and x = 0? a) mg cos θ ; mg cos θ ; x = (1 / 2)( g cos θ ) t 2 . b) mg cos θ ; mg sin θ ; x = (1 / 2)( g sin θ ) t 2 . c) mg sin θ ; mg sin θ ; x = (1 / 2)( g sin θ ) t 2 . d) mg sin θ ; mg sin θ ; x = (1 / 2)( g cos θ ) t 2 . e) mg sin θ ; mg sin θ ; x = ( g cos θ ) t . 005 qmult 01042 2 3 1 mod. math: dynamics and kinematics on a slope 2 41. A rigid frictionless slope has angle 30 ◦ . An object slides from rest for 10 s. About how far does it travel down the slope? a) 245 m. b) 424 . 35 m. c) 24 . 5 m. d) 42 . 44 m. e) 490 m. 005 qmult 01070 1 1 1 mod. thinking: reaction forces of a book Extra keywords: physci 42. A book sits at rest on a table. The reaction force that follows from Newton’s 3rd law to the gravitational force of the Earth on the book is the: a) gravitational force of the book on the Earth. b) normal (i.e., perpendicular upward) force of the table on the book.
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