HW Chapter 3
3.3 A web page designer creates an animation in which a dot on a computer screen has a
position of
r
= [4.0 cm + (2.5 cm/s
2
) t
2
]
i
+ (5.0 cm/s)t
j
. a) Find the magnitude and
direction of the dot’s average velocity between t = 0 and t = 2 s. b) Find the magnitude
and direction of the instantaneous velocity at t = 0, t = 1.0 s, and t = 2.0 s. c) Sketch the
dot’s trajectory from t = 0 to t = 2.0 s, and show the velocities calculated in part (b).
3.12 A daring 510N swimmer dives off a cliff with a running horizontal leap, as shown
in Fig. 1. What must her minimum speed be just as she leaves the top of the cliff so that
she will miss the ledge at the bottom, which is 1.75 m wide and 9.00 m below the top of
the cliff?
Fig. 1
3.19 A major league hits a baseball so that it leaves the bat at a speed of 30 m/s and at an
angle of 36.9
°
above the horizontal. You can ignore air resistance. a) At what
two
times is
the baseball at a height of 10.0 m above the point at which it left the bat? b) Calculate the
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 Spring '07
 D.V
 Velocity, radial acceleration, running horizontal leap, constant magnitude v2/R

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