Making Physics Out of the Ordinary
After I microwave food in a plastic container and remove the container from the oven, the container begins to shrink. It seems like there is a vacuum inside. The lid and all the sides of the container are squeezed inward. Why does this happen? U.S. You re right about the vacuum; the shrinkage you re seeing [ ]
A floating object is displacing fluids that would otherwise fill the space it occupies. For example, a ball floating motionless on water is displacing the water and air that would normally be where the ball is. If we remove the ball, water and air will fill its space and soon everything will be motionless again. [ ]
The earth receives heat from the sun at an incredible rate and, if it didn t get rid of that heat, it would get hotter and hotter. To maintain a steady average temperature, the earth must radiate away heat just as fast as it receives that heat from the sun. In other words, the thermal radiation [ ]
Why is it easier for a bicycle to stay upright when it is moving faster? And hard to stand up straight when it is moving slowly? What forces are acting on it that depend on its speed? A bicycle is an example of an object that is unstable at rest but stable in motion. That [ ]
How can a spinning object keep constant velocity with the direction of its parts changing at every instant? When you consider an object as rotating, you normally stop thinking of its parts as moving in their own independent ways and treat the whole assembly as a single object. While it s true that the various parts [ ]
When you push on a rotating object, when are you doing work? That s an interesting question and requires two answers. First, if you push on a part of the rotating object and that part moves a distance in the direction of the force you exert, then you do work on it. In principle, it is [ ]
When an object is rotating, both the up and down directions point along the vertical axis. Do they correspond to clockwise and counterclockwise? Yes. Distinguishing between the two opposite directions of rotation using words alone requires that everyone agree on what to call those two directions. It also requires that everyone have an artifact that [ ]
If you push someone on a swing with 50 N of force and they push back with 50 N of force, then why does the person still move? Shouldn t they stay motionless if all the forces are cancelled out? You re struggling with the most common misconception about Newton s third law of motion the law [ ]
Is deceleration something new or just acceleration in the opposite direction? Deceleration is simply a special case of acceleration. An object decelerates by accelerating in the direction opposite its current velocity. For example, if your car is heading toward Washington at 60 mph (100 km/h) and you push on the brake pedal, your car will [ ]
How can a basketball weigh 7.5 to 8.5 pounds when blown up but much less when deflated? What is it filled with when deflated? I will answer your question in two parts. First, the actual weight of a basketball is dominated by its skin and, which weighs about 22 ounces (about 1.4 pounds). The air [ ]