Question

The height meters of a mass projected vertically upwards at a time seconds s=ut-0.5gt².
Determine how long the mass will take after being projected to reach a height of 16m on the ascent.
b. on the descent when u=30m/s and g=9.8m/s​

Answer 1

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Answer:

  t ≈ 0.590 s (ascent); 5.532 s (descent)

Step-by-step explanation:

We are interested in the values of t when s=16.

  s = 30t -4.9t²

  4.9t^2 -30t +16 = 0 . . . . . substitute 16 for s; put in standard form

The quadratic formula can be used to find the solutions:

  t = (-(-30) ±√((-30)² -4(4.9)(16)))/(2(4.9))

  t = (30 ±√586.4)/9.8 ≈ 0.59023, 5.53221 . . . . seconds after launch

a) It will take 0.590 seconds to reach 16 m height initially.

b) It will take 5.532 seconds to return to 16 m height on descent.