We can break that diagonal motion down into horizontal and vertical portions; for now let’s just focus on the former. Say you start with a horizontal velocity (v1) of –1 meter per second and rebound with a horizontal velocity (v2) of +1 m/s. The change of sign indicates the reversal of direction. Think of it … Read more
However, since this force is applied at the feet, far from the center of mass (r > 0), it’s going to produce a torque. In this case, the torque would cause a forward angular acceleration, tending to deposit the jumper face down in the sand. So athletes use a few different techniques to counter this … Read more
A gymnast can actually perform both of these types of rotation at the same time—that’s what makes the sport so interesting to watch. In physics, we would call this type of movement a “rigid body rotation.” But, clearly, humans aren’t rigid, so the mathematics to describe rotations like this can be quite complicated. For the … Read more
When the elevator is stopped, the two forces are equal and opposite, and the net force is zero. But if you’re accelerating upward, the net force must also be upward. This means the normal force exceeds the gravitational force (shown by the lengths of the two arrows above). So you feel heavier when the normal … Read more
“How are matter and energy distributed?” asked Peter Schweitzer, a theoretical physicist at the University of Connecticut. “We don’t know.” Schweitzer has spent most of his career thinking about the gravitational side of the proton. Specifically, he’s interested in a matrix of properties of the proton called the energy-momentum tensor. “The energy-momentum tensor knows everything … Read more
But the solar system contains more than two masses. In fact, it started as a big cloud of dust without any planets and without the sun, and every speck of dust had an attractive interaction with every other speck. That’s a lot of complicated stuff going on, but there’s a trick we can use to … Read more
It’s been crazy cold this week, even down where I live in Louisiana, thanks to an outbreak of a polar vortex. This frigid air is bad for all kinds of things, including football helmets, apparently. But it’s actually a great time to demonstrate one of the basic ideas in science: the ideal gas law. You … Read more
