Physics 18 Spring 2011 Homework 7 - Solutions Wednesday March ...

(b) We want vf and Vf. Now, from the momentum equation, vf = Vf
v2 2
f = Vf − v2 i , and so we have V 2
f cos2 α
cos2 θ = v2 i + V 2
f , so
while
Vf =
vf =
So, plugging in the numbers gives
and
Vf =
vf =
vi cos θ
√ cos 2 θ + cos 2 α ,
vi cos α
√ cos 2 θ + cos 2 α .
5 cos 60
√ cos 2 60 + cos 2 30 = 2.5 m/s,
5 cos 30
√ cos 2 60 + cos 2 30 = 4.33 m/s.
6
cos α.
But
cos θ