Math CentralQuandaries & Queries


Subject: accelaration, velocity and displacement
Name: momo

a stone is thrown vertically downward with an initial speed of 14m/s from a height of 65 m above the ground. A) how far does the stone travel in the first 2.0 s? B) what is the stone velocity just before it hits the ground?

Hi Momo.

You are probably expected to ignore air friction and just use the acceleration due to gravity to solve this problem.

Gravitational acceleration is a constant for your situation - you should know the value of gravitational acceleration from your textbook.

A) The formula for displacement for an object under constant linear acceleration is

x = v0t + ½at2

where x is the displacement from the position at time t = 0, v0 is the initial velocity and a is the constant acceleration (gravitational acceleration). Use this formula to find the answer.

B) The formula for velocity under constant acceleration given the displacement x is

v2 = v02 + 2ax

Use this formula for part B.

Hope this helps,
Stephen La Rocque.

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