Does the design of balls (pentagons on soccer balls, lines on basketballs, panels on volleyballs, etc.) have a purpose or are they merely there for design?

In most cases they are simply design. However, they do affect the flow of air over the ball and will change its motion. The classic examples of balls with designs that matter are golf balls and baseballs. A golf ball has dimples because they dramatically change the airflow over the ball and allow it to travel much farther. We'll discuss that in a few weeks. A baseball's stitching also affects its flight from the pitcher to the mound and is very important to pitches like the knuckle ball and the spitball.

If you lifted an object with a hanging scale on earth and it read 15 N, would it read the same on Jupiter? What about the gravitational force pulling the object down? Wouldn't that alter the reading on the scale? Would you have to calibrate another scale to measure mass on Jupiter?

No, the scale would not read the same on Jupiter, and there would be nothing wrong with the scale! On Jupiter, the object would simply weigh more than on earth. Its mass wouldn't have changed and it would still contain the same number of atoms, but Jupiter would pull on it harder. As a result, the scale would have to pull upward on it harder and the scale would read a larger number of newtons. You wouldn't want to recalibrate the scale because it would be doing its job: it would correctly report that the object weighed about 40 N.

Is moment of inertia defined only by mass as inertia is in translational motion?

No, moment of inertia embodies both mass and its distribution about the axis of rotation. The more of the mass that is located far from the axis of rotation, the larger the moment of inertia. For example, a ball of dough is much easier to spin than a disk-shaped pizza, because the latter has its mass far from the axis of rotation.

What is the constant angular velocity of a stationary object on a flat surface?

If the object is fully stationary (not even spinning), then its angular velocity is zero. If it's spinning like a top, the its angular velocity is going to be pointing either up or down (depending on which way it's spinning) and of an amount that depends on just how hard its spinning. The unit of angular velocity is radians per second, where a radian is about 57 degrees. While degrees per second is easier to think about, the radian is the natural unit of angle (there are exactly 2 times Pi radians in a circle so that 2 Pi radians are 360 degrees).

What is angular velocity? The speed at which the ball is spinning?

Yes, angular velocity measures how quickly the ball is spinning. But it is more than that. I tells you both how quickly the ball is spinning (in radians per second), and the axis about which it's spinning, and whether it's spinning clockwise or counterclockwise about that axis. That's enough information to tell exactly how the ball is rotating.

How is it that gravity never stops, even in space. You said earlier that our weight would be zero in space. How can it be, if there's still gravity?

You've caught me some careless statements. Gravity really never stops, so that even if you were on the far side of the universe, the earth's gravity would still affect you. But that effect would be unimaginably small, so that you couldn't possible detect its presence. Because gravity weakens with distance, if you were to go to the depths of intergalactic space, many light years from any celestial object (other than perhaps a supermassive black hole), you would experience almost no gravity and would have almost no weight. But almost no weight isn't quite the same as exactly zero weight.

Why do some objects bounce off the ground (balls) whereas others would break (eggs)?

Some objects can deform elastically, storing energy in the process, while others can't. The surface of a rubber ball is made up of long, flexible molecules called polymers that can bend and stretch without breaking. As the ball's surface dents during an impact, these polymer molecules move about and begin to exert forces on one another (storing energy in the process), but they don't forget there original locations. As the ball rebounds, these molecules release their stored energy and push the ball back into the air. An egg, on the other hand, is made of hard, crystalline material that shatters during the deformation. Whole rows of atoms and molecules rip apart from one another and forget their origins. The egg doesn't store the impact energy. Instead, it turns that energy into thermal energy. The shell just crumbles.

Why do two objects of unequal mass fall and hit the ground at the same time?

If one object has twice the mass of the other, then it is twice as hard to accelerate. To make it keep pace with the other ball, it must experience twice the force. Fortunately, gravity pulls on it twice as hard (it has twice the weight of the other ball), so in falling, it does keep pace with the other ball. The two fall together. Just for fun, imagine stepping off the high diving board with two friends. The three of you have essentially identical masses and weights and also fall at the same rate. Now imagine that two of you hold hands as you fall. You are now a single object with twice the mass of your other friend. Nonetheless, you still fall at the same rate. So an object with twice the mass of another falls at the same rate as that other object.