fisica1-youn-e-freedman-exercicios-resolvidos

3.7: a)
b)
r ˆ ˆ
2
v = αi
− 2βtj
= (2.4 m s)ˆ i −[(2.4 m s ) t]ˆj
r
2 ˆ
2
a = − βj
= ( −2.4 m s ) ˆ. j
r
c) At t = 2.0s
, the velocity is v = ( 2.4 m s)ˆ i − (4.8 m s) ˆj
; the magnitude is
2
2
−4 .8
(2.4 m s) + ( −4.8
m s) = 5.4 m s , and the direction is arctan ( ) = −63°
. The
2. 4
2
acceleration is constant, with magnitude 2 .4 m s in the − y -direction. d) The velocity
vector has a component parallel to the acceleration, so the bird is speeding up. The bird is
turning toward the − y -direction, which would be to the bird’s right (taking the + z -
direction to be vertical).
3.8: