A projectile is fired straight upward with an initial veloc - ity of 100 m=s from the top of a building 20 m high and falls to the ground at the base of the building. Find (a) its maximum height above the ground; (b) when it passes the top of the building; (c) its total time in the air.

Question

Roxie

Physics

29 September, 14:54

A projectile is fired straight upward with an initial veloc - ity of 100 m=s from the top of a building 20 m high and falls to the ground at the base of the building. Find (a) its maximum height above the ground; (b) when it passes the top of the building; (c) its total time in the air.

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Answers (1)

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Brando · Answer 1

The answer to your question is:

a) h max = 529.7 m

b) t = 20.4 s

c) t = 20.6 s

Explanation:

a) h max = - (vo) ² / 2g

= 100² / 2 (9.81)

= 10000 / 19.62

= 509.7 m

total height = 509.7 + 20 = 529.7 m

b)

h = gt² / 2

t = √ 2h / g

t = √ 2 (509.7) / 9.81

t = √ 103.91

t = 10.19 s

total time = 2 x t = 2 x 10.19 = 20.4 s

c)

h = vot + 1/2gt²

20 = 100t + 1/2 (9.91) t²

4.9t² + 100 t - 20 = 0 quadratic equation

t = 0.19 s

Total time = 0.19 + 20.4 = 20.6 s