An orange object moves across a
grid of lines spaced one meter apart. The object moves for two
seconds. The arrow shows the distance that
the object moves in each second. What is the speed of the object
relative to the grid lines that it crosses?
Here, we are asked to find the
speed of an object relative to a grid line that the object crosses. All the grid lines are
stationary. This means that the motion of an
object toward or away from a grid line is the only thing that affects the speed of
the object relative to the grid line.
We see then that our equation for
speed will just depend on the change in distance of the object. Remember that the speed of an
object is the distance traveled by the object divided by the time that the object
Looking at this diagram, we can see
that in the two seconds that the object is moving, it has traveled past two grid
lines. These lines are spaced one meter
apart. This means that the object traveled
two meters in two seconds.
Now let’s look at our equation for
speed and substitute these values. Speed is equal to distance
traveled, two meters, divided by the time it takes to travel that distance, two
seconds. So the speed is equal to two meters
divided by two seconds. Simplifying this will give us the
speed of one meter per second. This is the speed of the object
relative to the grid lines that it crosses.