ch04-p117 - 117. The (box)car has velocity vc g = v1 i...

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117. The (box)car has velocity G vv cg i = 1 # relative to the ground, and the bullet has velocity G v bg 02 2 i j =+ cos # sin # θθ relative to the ground before entering the car (we are neglecting the effects of gravity on the bullet). While in the car, its velocity relative to the outside ground is G v bg 08 2 .c o s # # i 0.8 j 2 (due to the 20% reduction mentioned in the problem). The problem indicates that the velocity of the bullet in the car relative to the car is (with v 3 unspecified) G bc j = 3 # . Now, Eq. 4-44 provides the condition 22 3 1 ˆˆ ˆ ˆ 0.8 cos i 0.8 sin j j i v v v += + GG G so that equating x components allows us to find θ . If one wished to find v 3 one could also equate the y components, and from this, if the car width were given, one could find the time spent by the bullet in the car, but this information is not asked for (which is why the width is irrelevant). Therefore, examining the x components in SI units leads to
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