Question

Of the following five descriptions, which one could not be representing a projectile motion correctly?

First row, first picture.
First row, second picture.
Second row, first picture.
Second row, second picture.
Second row, third picture.
None of them.
All of them would be ok.

Answer 1

Answer: Second row, second picture.

Reason:

As the object falls, gravity accelerates it to speed up to a faster vertical velocity. This will make the
`\text{V}_{\text{y}}` increase in negative value, as indicated by the graph in the upper left corner. The graph in the bottom right corner also indicates this with the longer arrows pointing downward.

Unfortunately, the table in the second row, second picture is incorrect because the
`\text{V}_{\text{y}}` value mistakenly remains constant. The -9.8 is the acceleration and not the velocity.

The horizontal velocity is constant because there aren't any forces pulling left or right on the projectile object. This assumes we ignore air resistance.