Question

An object is thrown straight down from the top of a building at a speed of 20 m/s . It hits the ground with a speed of 40 m/s.

1. How high is the building ?
2. How long was the object in the air ?


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Answer 1

Answer:

☆$\textbf{Here is your answer}$

Explanation:

● Sol :-

u = 20 m/s , v = 40m/s

acceleration = v - u / t

》》》》》a = 40 - 20/ t

》》》》》at = 20/t m/s^2

then,

from newton's formula,

》》s = ut + 1/2at^2

》》s = 20t + 1/2 × 400

》》 s = 20t+200 equation 1

then,

Newton's formula,

》》v^2 - u^2 = 2as

》》 1600 - 400 = 40(20t + 200)/t

》》 1200t = 800t + 8000/t

》》 1200t - 800t = 8000

》》 400t = 8000

《》 t = 20s

then,

putting the value of t in equation 1

s = 600m

And 2 answer that is time = 20s