Velocity vs Time: Dropped Ball Analysis

[goonking]

Homework Statement

http://imgur.com/FJzyuSY

Homework Equations

The Attempt at a Solution

since the graph is velocity and time, i believe the slope SHOULD be distance or placement, correct?

and 1 ball is dropped above the ground so I assume the answer is B since it has a line starting above the 0.

and it makes sense since the slopes are curved because acceleration due to gravity will make the slopes curved, is this correct?

 

[tony873004]

Slope is rise over run. Your rise is velocity, and your run is time. What is velocity / time? That's your slope.

 

[goonking]

Slope is rise over run. Your rise is velocity, and your run is time. What is velocity / time? That's your slope.

oooh, the slope is acceleration.

 

[goonking]

if you throw straight down something instead of dropping it, is it still in free fall? is the acceleration greater than the force of gravity?

 

[tony873004]

Acceleration near the surface of the Earth is considered constant. Earth will not pull any harder on the object with initial velocity. The only difference between the object dropped and the object thrown straight down is that the object dropped has 0 initial velocity and the object thrown has negative initial velocity. Knowing that should eliminate 3 of your choices.

 

[goonking]

is the answer D? because the slopes are constant so acceleration is constant which is true because force of gravity doesn't change, it will always be -9.8 m/s^2.

but it also doesn't make sense because if a object is dropped from free fall, its initial velocity should be at 0.

 

[tony873004]

No the answer is not D. Sure the slopes are constant in D, but they're a constant 0. We know that on Earth they should be a constant -9.8.
There's another graph with constant slopes. (Hint: constant means straight line, whether its horizontal like D, or sloped).

 

[goonking]

ahhh, so the answer is A because the slope is a negative value.

 

[tony873004]

Yes! And they both have the same negative slope since gravity accelerates each one equally, and the top one begins with 0 velocity because it was dropped, and the bottom one begins with negative velocity because it was thrown.