An object moving along a straight line has v = -7 m/s. What does this velocity say?
You've already seen that a velocity's sign gives its direction: v = −3 m/s means moving in the negative direction at 3 m/s. Acceleration has a sign of its own too, and it is easy to misread.
Follow the cart's readings. It starts at +5 m/s. One second on, it reads +3 m/s. The velocity has changed by 2 m/s toward the negative direction.
The change keeps going: +1 m/s, then −1 m/s. The cart's velocity passes zero and turns negative. The acceleration never changed.
By 4 s the cart moves ever faster in the negative direction. The same a = −2 m/s² held the whole run. First it slowed the cart, then it sped the cart up.
An object has an acceleration of -6 m/s². What does that tell you about its motion?
The mirror image runs the same way. With a = +2 m/s², the cart's velocity changes by 2 m/s toward the positive direction each second: −5, −3, −1, +1, +3 m/s.
A hockey puck has an acceleration of +3 m/s². The plus sign gives the direction of the velocity change: the puck's velocity changes by 3 m/s toward the positive direction each second.
A subway train has an acceleration of −4 m/s². Does the minus sign mean the train is slowing down? It does not have to. The sign means the train's velocity changes by 4 m/s toward the negative direction each second. Whether that slows the train depends on which way the train is already moving.
A gondola has an acceleration of +2 m/s². Which statement must be true?
A shuttle bus has an acceleration of -3 m/s². Which list could be its velocity at one-second intervals?
An object's velocity at one-second intervals reads +2, -1, -4 m/s. What is the sign of its acceleration?
A cyclist moving in the negative direction has an acceleration of -2 m/s². A classmate says the minus sign on the acceleration shows the cyclist is slowing down. What does that sign actually show?