Take the right as positive. For each case, say whether the body is speeding up or slowing down, and…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Take the right as positive. For each case, say whether the body is speeding up or slowing down, and which way it is moving.
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Need a reminder? The key ideaShow
Along a line, a body speeds up when its velocity and acceleration have the same sign, and slows down when the signs differ. The sign of the velocity alone gives the direction of motion.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Use the sign rule, then check with one second later.
Step 1. Case (a). Same signs: speeding up, to the right ().
Step 2. Case (b). Opposite signs: slowing down, to the right ().
Step 3. Case (c). Same signs: speeding up, to the left (, larger in size).
Step 4. Case (d). Opposite signs: slowing down, to the left ().
Answer: (a) speeding up, right. (b) slowing down, right. (c) speeding up, left. (d) slowing down, left.
Watch out. Case (c) has a negative acceleration and yet speeds up. "Negative acceleration means slowing down" is the slip this problem is built to catch.
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