If a toy rocket accelerates to a velocity of 25 meters per second in 3 seconds, what is its acceleration?

Answer 1

Knowing the definition and units of things is a big help, and sometimes help you not to have to memorize so many things.

You know what acceleration is just by riding in a car. When the car is accelerating it is speeding up. It is changing it's speed, or velocity. If you speed up a lot on a short amount of time, you've accelerated a lot. If you speed up slowly, you would say you have a slow acceleration. Try to relate what you are learning to real life - it helps you learn and remember. From what we've talked about here,hopefully it makes sense that acceleration is the change of speed (velocity) over time. Now think about units: change in velocity over time, is (m/s)/s, which simplifies to m/s². It is good to be able to recognize that m/2 is a velocity and m/s² is an acceleration. Knowing the units often points to the formula, and vice versa.

So in this problem you have a toy rocket. We will assume at the beginning the rocket is still, so it has a velocity of 0. Three seconds later, according to the story, it has a velocity of 25 m/s. The change in velosity is 25-0 = 25 m/s. This took 3 sec to do.

So the problem is set up as

((25-0) m/s) / (3 s)

Good luck!

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In the above I've loosely used velocity and speed interchangeably. They are not really the same. Velocity is used when we have a speed AND a direction. In the case of the toy rocket, I will hope that direction is "up". Speed doesn't need to have a direction specified.