Question

A car is driving in the negative X direction at a steady speed of 15 m/s. if it starts at a position of 30m:

What is its displacement in the first second? My answer was 15m and used Xf-Xo (final-initial) to find the displacement
What is his displacement in the first two seconds? 30m
Where is it at time of 1 second? 15m
Where is it at a time of 2 seconds?30m

Am I doing this correct or what equations should I use?

Answer 1

You need to use the velocity, since distance = speed * time

The speed is -15 m/s, so after t seconds, starting from x=30,

x = 30 - 15t

So, you are correct that x(1) = 15, but after 2 seconds,

x(2) = 30 - 15*2 = 0
The object has indeed moved 30m after 2 seconds, but it has moved back to the 0 coordinate.