Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!
Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for K-8 and here for K-12.
Please login or register to read the rest of this content.
Please login or register to read the rest of this content.
Thank you, that makes sense now!
Yes, gravity can do work, but since gravity and the chair’s movement are in the same direction, there’s no work done on the chair by gravity. If the chair was moving upwards against the pull of gravity, then gravity would be doing work on the chair.
In this case, you could say that there is work done by friction of the air molecules against the chair as it falls through the atmosphere, because friction forces oppose the motion.
The answer to question 5 (in the energy exercise) says that no work was being done on the chair while it’s falling because the chair was not being moved against a force. I was wondering, isn’t gravity working against air resistance to cause the chair to fall? And if so isn’t gravity moving the chair a distance (from the top of the roof to the ground) against a force (air resistance)?