Calculate Velocity

Question

Suppose a paper ball is shot from 5 feet off the ground and the paper ball reaches a height of 10 feet after 3 seconds. Calculate the velocity of the ball.

Answer 1

Velocity = Distance Travelled / Time => (10 - 5) feet / 3 sec => 5/3 feet/sec => 1.667 feet/sec => this is the velocity of the ball at 10 feet from the ground.

There is gravitational pull acting on the ball which is deceleration and that is reducing the ball's velocity but that's out of scope of the question. Just mentioning this since there might be some follow-up questions related to that as paper ball is shot upwards and that fact was never used in this question.

Answer 2

Given:

Paper ball shot into the air.

ho = Initial height = 5 ft

After 3 seconds, height = 10 ft.

Find: Velocity.

Solution:

Recall: acceleration due to gravity = -32 ft/sec^2

h = ho + v*t - (1/2)a*t^2

10 = 5 + v(3) - (16)(3)^2

10 = 5 + 3v - 16*9

10 = 5 + 3v - 144

10 = -139 + 3v

149 = 3v

v = 149/3 = 49.67 ft/sec.