Question

2. A ball is hit off a cliff with an initial velocity of 20m/s. The cliff is 100 m high. How many seconds does the ball take to reach the ground?

a. 4.5
b. 20
c. 9.8
d. 2.0

Answer 1

option d is correct

Step-by-step explanation:

We use the formula;

`v_(f)` =
`v_(i)` +
`at`

Where:

`v_(f)` = 0 m/s ( because when it reaches the ground its final velocity would be zero)

`v_(i)` = - 20 m/s ( the negative sign shows its free falling downwards)

a = g = 9.8 m/
`s^(2)` ( a free falling body experiences acceleration due to gravity)

substituting the values in the formula;

0 = - 20 + 9.8t

20 = 9.8t

20/9.8 = t

2.041 ≈ 2.0 s = t