ch04-p114 - 114 We neglect air resistance which justifies...

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114. We neglect air resistance, which justifies setting a = – g = –9.8 m/s 2 (taking down as the – y direction) for the duration of the motion of the shot ball. We are allowed to use Table 2-1 (with Δ y replacing Δ x ) because the ball has constant acceleration motion. We use primed variables (except t ) with the constant-velocity elevator (so '1 0 m / s v = ), and unprimed variables with the ball (with initial velocity 0 20 30 m/s vv =+ = , relative to the ground). SI units are used throughout. (a) Taking the time to be zero at the instant the ball is shot, we compute its maximum height y (relative to the ground) with 22 00 2( ) g y y =− , where the highest point is characterized by v = 0. Thus, yy v g =+ = o m 0 2 2 76 where oo 23 0 m = (where o 28 m y ′ = is given in the problem) and v 0 = 30 m/s relative to the ground as noted above. (b) There are a variety of approaches to this question. One is to continue working in the frame of reference adopted in part (a) (which treats the ground as motionless and “fixes”
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This note was uploaded on 05/17/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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