fisica1-youn-e-freedman-exercicios-resolvidos

3.64: Combining equations 3.25, 3.22 and 3.23 gives
2 2 2
v = v cos α + ( v sinα
− gt)
0
= v
= v
2
0
2
0
2
0
0
− 2g(
v
− 2gy,
0
0
0
2
2
= v (sin α + cos α ) − 2v
sinα
gt + ( gt)
0
0
1
sinα
0t
− gt
2
where Eq. (3.21) has been used to eliminate t in favor of y. This result, which will be seen
in the chapter dealing with conservation of energy (Chapter 7), is valid for any y,
positive, negative or zero, as long asv
2 > 0 . For the case of a rock thrown from the roof
of a building of height h, the speed at the ground is found by substituting y = −h
into the
above expression, yielding v = 2
v + 0
2gh
, which is independent of α
0
.
2
)
0
2
0
2