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fisica1-youn-e-freedman-exercicios-resolvidos

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v y .<br />

g<br />

2<br />

9.80 m s<br />

0 16.0 m s<br />

3.18: a) The time t is = = 1.63 s<br />

2<br />

v<br />

=<br />

0<br />

2 y0<br />

2g<br />

=<br />

1 2<br />

b) 1<br />

y<br />

gt v t = 13.1 m .<br />

2<br />

c) Regardless of how the algebra is done, the time will be twice that found in part (a),<br />

or 3.27 s d) vx<br />

is constant at 20 .0 m s , so ( 20.0 m s)(3.27 s) = 653 . m .<br />

e)<br />

3.19: a) v = (30.0 m s)sin 36.9°<br />

18.0 m s ; solving Eq. (3.18) for t with y 0 and<br />

y = 10.0 m gives<br />

0 y<br />

=<br />

2<br />

(18.0 m s) ± (18.0 m s) − 2(9.80 m s )(10.0 m)<br />

t =<br />

= 0.68 s,2.<br />

99 s<br />

2<br />

9.80 m s<br />

b) The x-component of velocity will be ( 30.0 m s)cos36.9° = 24.0 m s at all times.<br />

The y-component, obtained from Eq. (3.17), is 11 .3 m s at the earlier time and<br />

− 11.3 m s at the later.<br />

c) The magnitude is the same, 30 .0 m s , but the direction is now 36 .9°<br />

below the<br />

horizontal.<br />

2<br />

0 =

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