85.1 Newtons first law of motion and the concept of force 4. Some common forces ① Normal force of a surface.(§5.10 Tensions in ropes, strings, and cables; (8 5.11) 3 Static friction and kinetic friction;($5.12-5.13 85.2 Newton's second law and third law of motion 52 Newton's second law of motion and Newton's third law of motion 1. Newton's second law of motion and its aspects Protal=ma E-ma=.=ma, or F_=mam F= mat P176-177 F,total=ma A force of magnitude 1n on the standard kilogram produces an acceleration of magnitude Im/s2 1N=1 kg m/s23 4. Some common forces 1 Normal force of a surface. (§5.10) 2 Tensions in ropes, strings, and cables;(§5.11) 3 Static friction and kinetic friction; (§5.12~5.13) §5.1 Newton’s first law of motion and the concept of force §5.2 Newton’s second law and third law of motion §5.2 Newton’s second law of motion and Newton’s third law of motion 1. Newton’s second law of motion and its aspects A force of magnitude 1 N on the standard kilogram produces an acceleration of magnitude 1m/s2. 1 N=1 kg·m/s2 P176-177 ⎪ ⎩ ⎪ ⎨ ⎧ = = = = ⇒ z z y y x x F ma F ma F ma F ma ,total ,total ,total total r r ⎩ ⎨ ⎧ = = = t t n n F ma F ma F ,total ,total r or