at a certain instant, a toy rocket is observed to have a velocity v=(5i+12j)m/s?

Question

a) has it already reached maximum height? Explain your answer
B)what is its kinetic energy at maximum height if the mass of the projectile is 2kg?

Answer 1

Assuming vj is vertical vel., then since vj > 0, we're not at max height yet. At max height vj = 0, so KE = m*vi^2/2.