wow...Phys...this has me COMPLETELY clueless
posted by Kimlee .
it is a projectile motion question i just can't seem to figure out
A ball is shot from the ground into the air. At a height of 9.1 m, its velocity is observed to be v = 7.6i + 6.1j m/s
To what maximum height does the ball reach?
the answer is suppose to be 11m

The vector velocity component that goes with the "j" unit vector is the vertical component. At 9.1 m height, the ball will rise until the vertical component becomes zero. That additional height H can be obtained from energy considerations:
g H = (1/2)(6.1 m/s)^2
which tells you that
H = 1.9 m
Add that to 9.1 m for the answer.