# Anti-Gravity in projectiles

In the vertical xy plane a particle is projected with a velocity $$10 m/s$$ making an angle $${ 45 }^{ 0 }$$ with the $$+ve$$ x-axis. Acceleration due to gravity is $$-10j m/{ s }^{ 2 }$$.

At time $$t=\alpha$$ sec the anti-gravity switch is turned on. Now the acceleration is $$10j m/{ s }^{ 2 }$$. If the particle passes through the point $$(30, 20)$$ during it's motion then: Find $$\alpha$$.

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