velocity and acceleration?

Question

Need help, ive been working on this problem all day, please just help me!

A particle leaves its origin with a velocity of 4 i m/s and a constant acceleration of ( -2 i + .5 j ) m/s^2. At the time the particle reaches its maximum X coordinate (a) what is the velocity? (b) what is its position vector?

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Answer 1

ax=acceleration in x direction=-2
ay=acceleration in y direction=0.5
V1x=initial velocity in x direction= 4
V1y=initial velocity in y direction=0
At the time the particle reaches its maximum X coordinate, velocity in x direction is zero(V2x = 0)

a)
V2x = ax * t + V1x then t= - V1x / ax
t=2
V2y=ay * t + V1y
V2y=0.5 * 2 = 1
velocity in x direction is zero so the answer for part (a) is 1

b)
x=1/2 * ax * t^ 2 + V1x * t
x=4
y=1/2 * ay * t^ 2 + V1y * t
y=1