The cork flew out of the bottle vertically upward at a speed of 20 m / s and is in free fall.

| June 16, 2021 | education

The cork flew out of the bottle vertically upward at a speed of 20 m / s and is in free fall. What speed will it have when it rises 15 m? How long will it take?

V0 = 20 m / s.

g = 9.8 m / s ^ 2.

h = 15 m.

V -?

t -?

1 way.

Let’s use the law of conservation of total mechanical energy.

Ek0 = En + Ek.

m * V0 ^ 2/2 = m * g * h + m * V ^ 2/2.

V0 ^ 2/2 = g * h + V ^ 2/2.

V ^ 2 = V0 ^ 2 – 2 * g * h.

V = √ (V0 ^ 2 – 2 * g * h).

V = √ ((20 m / s) ^ 2 – 2 * 9.8 m / s ^ 2 * 15 m) = 10.3 m / s.

Method 2.

The plug moves under the action of gravity with the acceleration of gravity g.

For equally slow motion, the lifting height h is determined by the formula: h = (V0 ^ 2 – V ^ 2) / 2 * g.

V0 ^ 2 – V ^ 2 = 2 * g * h.

V ^ 2 = V0 ^ 2 – 2 * g * h.

V = √ (V0 ^ 2 – 2 * g * h).

V = √ ((20 m / s) ^ 2 – 2 * 9.8 m / s ^ 2 * 15 m) = 10.3 m / s.

t = (V0 – V) / g.

t = (20 m / s – 10.3 m / s) / 9.8 m / s ^ 2 = 0.98 s.

Answer: the speed of the plug will be V = 10.3 m / s, t = 0.98 s.



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