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Unformatted text preview: Newton’s First Law: In the absense of a net external force (Net force=total force=∑ F) (sitting in seat, car moving const speed) Newton’s Second Law: F(Net)=ma (object accels in same direct as F(Net) Newton’s Third Law: When two objects react they exert equal and opposite forces on each other (action=reaction) A 1000kg car accels 1m/s 2 What force is required for it to accelerate at this rate? F=ma F= (1000kg)(1m/s 2 ) F=1000N 1N= 1kg(m) / s 2 A force of 3000N in the horizontal directions acts on 1000kg car. What’s the acceleration? F=ma a=F/m a=3000N/1000kg= 3m/s 2 Weight= mass/ acceleration 1N= .225lb In a grocery store you push a 12.5 kg shopping cart with a force of 14N. if it starts at rest how far does it move in 3s? F=ma a=f/m= 14N/12.5kg= 1.12m/s 2 ∆x=V i (t)+(1/2)at 2 ∆x=0+(1/2)at 2 ∆x =(1/2)(1.12)(3 2 )= 5.04m If object 1 exerts a force F on object 2, then object 2 exerts a force –F on object 1 !!! Forces always act on different objects and do not cancel! 64kg parent and 16kg child meet at center of ice rink. Put hands together and push. a) force experienced by child is same as experienced by parent b) acceleration of child is greater because of a smaller mass to keep forces equal c) magnitude of parent’s acceleration? -0.6s F(child)= F(parent) ma(child)=ma(parent) a(parent)= (16)(2.6)/ (64) = 0.6s (the mag is neg b/c child moves pos, parent moves pos)...
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