# 2D Kinematics Question

I assume I will be using V = V(initial)+at and r=r(initial) + v(initial)*t +1/2at^2 for both the x and y component.

Here is my attempt.

for the antitank gun:

rx = 0 + 240cos(10)t

ry = 0 = 60 +240sin(10)t – 4.9t^2

t = -1.21s, 9.76s, ignoring the negative for this problem.

to find final position of missile rx = 240cos(10)(9.76s) = 2306.81m

for the tank:

r(Tank) = 2200+0+.5t

2306.81 = 2200+0+.5t

t = 213.63 sec for the tank to get from where it started to where the missile will hit it.

Since it takes 9.76 for the missile to arrive I would have though it would need to take off 213.63 s – 9.76 s after the tank starts moving.

The answer sheet says 9.8sec , I’m assuming rounding up from the 9.76 missile flight time. Could someone explain the logic to me? Why should I stop at just the tank flight time.

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