Question

A book is thrown downward from the library window with a speed of 2.0 s m and lands on the ground 5.0 m. We can ignore air resistance. What is the final velocity of the book in m/s?

Answer 1

Answer:

4.5m/s

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Explanation:

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Answer 2

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‎ ‎‎‎‎Final Speed V(t) is given as

V(t) = u + at .........(1)

Where,

u = initial speed.

a = acceleration

t = time taken.

The Total Distance travelled 'd' is given as

$d \: = ut + \frac{1}{2} a {t}^{2}$

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d = 5.0 m

u = 2.0 m

a = g = 10 ......(acceleration due to gravity)

Substituting into the equation above we have..

$5 = 2t + 5 {t}^{2} \\ 5 {t}^{2} + 2t - 5 = 0$

Applying the quadratic formula. we have,

t = 0.82 s or t = -1.22 s

t cannot be negative

Therefore,

ㅤㅤㅤㅤㅤㅤt = 0.82 s

From Equation (1)

$v = 2 + 10(0.82) \\ v = 2 + 8.2 \\ v = 10.2$

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