Question

Disregarding air resistance, what is the speed of a ball dropped from 12 feet just before it hits the ground? (Use 1 ft = 0.30

m, and use g = 9.8 m/s2)
2.4 m/s
8.4 m/s
10.8 m/s
15.3 m/s

Answer 1

B - 8.4 m/ is the correct answer.

Answer 2

Answer: 8.4 m/s

Step-by-step explanation:

This described situation is related to vertical motion (free fall), with constant acceleration (acceleration due gravity), and in this case, the following formula will be useful:

`{V_(f)}^(2)={V_(o)}^(2)+2ad` (1)

Where:

`V_(f)` Is the final velocity of the ball

`V_(o)=0` Is the initial velocity of the ball (it was dropped)

`a=9.8 m/s^(2)` is the acceleration due gravity

`d=12 ft=3.6 m` is the distance at which the ball hits the ground (taking into account
`1 ft=0.30 m`,
`12 ft (0.30 m)/(1 ft)=3.6 m`)

`{V_(f)}^(2)=0+2(9.8 m/s^(2))(3.6 m)` (2)

`V_(f)=\sqrt{2(9.8 m/s^(2))(3.6 m)}` (3)

Finally:

`V_(f)=8.4 m/s`