An object moving along a straight line has v = -7 m/s. What does this velocity say?
A warehouse cart rolls down a straight aisle at 3 m/s for 2 s. Then a worker turns it around and sends it back the other way: by t = 5 s the cart is moving at 6 m/s in the negative direction, velocity −6 m/s, and it keeps that up until t = 8 s. Forward, then backward. The trip's picture shows which is which at a glance.
You've already seen that the sign of a one-dimensional velocity is the direction of motion. The graph shows that sign at a glance. The time axis sits at v = 0, so every point above it is a positive velocity, and every point below it is a negative one.
The graph shows the velocity of a forklift. In which direction is the forklift moving at t = 7 s?
One thing tries to fool you here: whether the line is rising or falling. Watch it fail twice.
The graph shows the velocity of a mine cart. In which direction is the cart moving at t = 4 s?
At t = 4 s the line lies below the time axis, so the velocity is negative.
A negative velocity means motion in the negative direction, even though the line is rising.
The cart is moving in the negative direction.
The graph shows the velocity of a glider. In which direction is the glider moving at t = 3 s?
At t = 3 s the line lies above the time axis, so the velocity is positive.
A positive velocity means motion in the positive direction, even though the line is falling.
The glider is moving in the positive direction.
The mine cart's line was rising, and the cart was moving in the negative direction. The glider's line was falling, and the glider was moving in the positive direction. Rising and falling say nothing about the direction of motion. Only the side of the axis does.
The graph shows the velocity of a canoe. In which direction is the canoe moving at t = 5 s?
The graph shows the velocity of a street sweeper. In which direction is the sweeper moving at t = 6 s?
One last case: a stretch where the line runs along the time axis itself. There the velocity is 0 m/s, so the object is not moving during that stretch.
The graph shows the velocity of a warehouse robot. In which direction is the robot moving at t = 5 s?
The graph shows the velocity of a rover. What is the rover doing at t = 6 s?
The graph shows the velocity of a patrol boat over 9 s. At which of these times is the boat moving in the negative direction?