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a person uses a slingshot to launch a rock upward with a velocity of 30m/s how long does it take to reach a height of 20m what...Asked by wayne
a boy uses a sling shot to launch a rock upward with a velocity of 30m/s how long does it take to reach a height of 20 m what maximum height does the rock reach, what is the velocity of the rock at this height, what is the velocity of the rock just before it lands
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Answered by
Scott
h = ½ g t² + 30 t = -4.9 t² + 30 t
substitute 20 for h to find the time
... use the quadratic formula
the time of max h is on the axis of symmetry of the parabola
... t = -b / 2a = -30 / -9.8
... plug in the time to find h max
the velocity is zero at max h
the impact velocity equals the launch velocity (but opposite direction)
... this ignores the height of the launcher and air resistance
substitute 20 for h to find the time
... use the quadratic formula
the time of max h is on the axis of symmetry of the parabola
... t = -b / 2a = -30 / -9.8
... plug in the time to find h max
the velocity is zero at max h
the impact velocity equals the launch velocity (but opposite direction)
... this ignores the height of the launcher and air resistance