22 Motion in One DimensionQ2.8Yes. If you drop a doughnut from rest v=0af, then its acceleration is not zero. A commonmisconception is that immediately after the doughnut is released, both the velocity and accelerationare zero. If the acceleration were zero, then the velocity would not change, leaving the doughnutfloating at rest in mid-air.Q2.9No: Car A might have greater acceleration than B, but they might both have zero acceleration, orotherwise equal accelerations; or the driver of B might have tramped hard on the gas pedal in therecent past.Q2.10Yes. Consider throwing a ball straight up. As the ball goes up, itsvelocity is upward v>0af, and its acceleration is directed downa<0af. A graph of vvs. tfor this situation would look like the figureto the right. The acceleration is the slope of a vvs. tgraph, and isalways negative in this case, even when the velocity is positive.vtv0FIG. Q2.10Q2.11(a)Accelerating East(b)Braking East(c)Cruising East(d)Braking West(e)Accelerating West(f)Cruising West(g)
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