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Writer's picturekeshprad

PhysicsBowl 2016 Q21


21) For this problem, we are going to want to find the projectile's launch angle. We are told that the minimum speed of the projectile is 15.0 m/s and occurs 1.94 seconds from the launch.


Let's figure out when a projectile travels at its minimum speed.

Where v is velocity

Since we can assume negligible air resistance, v[x] is a constant. Thus, we can find our minimum speed when the magnitude of v[y] is minimized. This happens at the max-height, where v[y] is 0 m/s.


From this point, knowing acceleration due to gravity, the time it takes to reach max-height, and v[y] at max-height, we can find the initial vertical velocity.

Where v is velocity, t is time, a is acceleration, and g is acceleration due to gravity

Finally, since we have the initial velocity in the x-direction and y-direction, we can use basic trigonometry to find the angle of incline.

Answer: B

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