Question

@thesmartone

Answer 1

A ball is kicked from a location <12, 0, -12> m (on the ground) with initial velocity <-16, 13, -8> m/s.

First part:
What is the velocity of the ball 0.5 seconds after being kicked?

I got <-16, 8.1, -8>m/s which was correct

Second part:

What is the location of the ball 0.5 seconds after being kicked?

Answer 2

putting a pic of my work in a sec

Answer 3

It says the x and z components are correct on the second part, but not the y

Answer 4

@SmokeyBrown ?

Answer 5

So the problem is that the velocity of the ball after 0.5 seconds is not the same as the *average* velocity across that time. The calculation you used would be correct for the average velocity, but you only used the final velocity.
Now, since we know the initial velocity and the final velocity, and we know that the acceleration is constant, the average velocity, should be the sum of those two values divided by two.

Answer 6

Ooohhhh, that makes sense. That was throwing me off though because in the example the book gave, they used the final velocity as the average

Answer 7

No problem, that does sound pretty confusing.
The final velocity can be the same as the average, if the velocity stays constant, or if the velocity increases and decreases. In this case, as you've seen, the velocity constantly decreases

Answer 8

Gotcha, thanks for the help

Answer 9

Absolutely!