Question

a cricket ball is dropped from a height of 20 m calculate the speed of ball ball when it hits the ground calculate the time takes to fall through this height gravitation is per second square

Answer 1

initial velocity = 0m/sec
Height ( s)= 20m
a= 10 m per sec square
final velocity = 2as= v sq. - u. sq.
2×10×20= v sq
v=20m per sec sq.
time= v = u+at
20= 0 + 10t
10t = 20
so t = 2 sec

Answer 2

Answer:

2 seconds

Explanation:

Initial Speed(u) = 0

Final Speed(v) = ?

Acceleration due to gravity(a) = 10 m/s^2

Height(h) = 20 m

We know that for a freely falling body :

$\implies \sf \: {v}^{2} = {u}^{2} + 2gh$

$\implies \sf \: {v}^{2} = ( {0)}^{2} + 2 \times 10 \times 20$

$\implies \sf \: {v}^{2} = 0 + 400$

$\implies \sf \: {v}^{2} = 400$

$\implies \sf \: {v} = \sqrt{400}$

$\implies \sf \: {v} = 20m {s}^{ - 1}$

Thus, The speed of ball will be 20 metre per second.

Now, Let's find time ;)

$\implies \sf \: {v}= {u}+gt$

$\implies \sf \: 20= 0 + 10 \times t$

$\implies \sf \: 20= 10t$

$\implies \sf \: t = \cancel\dfrac{20}{10}$

$\implies \sf \: t = 2 \: seconds$

Hence, The ball takes 2 seconds to fall through the Height of 20 metres.