How Does Gravity Affect a Stone Thrown Downward?

[bryans1mic]

hello there, i had a question about a free fall question.

Problem states that a stone is thrown vertically downward with an initial
speed of 12.0 m/s from some tower.

well, i was wondering if i should use 12.0m/s or if i should use gravity (9.8 m/s)

will the rock have an initial speed of 12.0m/s then eventually become 9.8 m/s
or will it be 12.0 m/s until the rock hits the ground.


(all my book examples were throwing something upwards which is manageable but
going downward gots me stumped.)

thanks

 

[cepheid]

Hi bryans1mic, welcome to PF!

Be careful not to confuse velocity (m/s) with acceleration (m/s²). Objects in free fall (i.e. under the influence of gravity *only*) will accelerate downward at 9.8 m/s². What this means is that although the object will start out with a velocity (initially) of 12.0 m/s downward, gravity will accelerate the stone so that its downward velocity increases (that's what acceleration is...the rate of change of velocity). Its velocity will increase by 9.8 m/s PER second. That's where the unit of m/s² for acceleration comes from.