Now the ball behaves extra such as you would count on. Its horizontal velocity decreases in order that it falls behind the unique automobile. Nevertheless it’s nonetheless not going to hit your windshield. With air drag and lack of power on impression with the bottom, every bounce is a little bit decrease than the one earlier than. You ought to be superb.
Rock Out
Now say that child drops a rock out the window. Children! Or possibly there’s a truck carrying gravel, and a few of it slips by means of a crack. When the rock hits the highway, its movement can change in a number of methods. First, there is a frictional power between the rock and the highway, which is able to scale back the rock’s horizontal velocity. As we noticed above, slower is dangerous.
Second—and this may appear bizarre—as a result of a rock is irregularly formed, it is doable that it spins and hits the pavement in a means that makes it skip up larger than it began.
Maintain on! Isn’t {that a} violation of the regulation? , the regulation of conservation of power? Nope, it’s an power switch. A rotating and transferring rock has each rotational and translational (linear) kinetic power. Some collisions can convert rotational power to translational power, which makes the rock bounce larger. Increased is dangerous.
This is what that may appear to be:
So that you’re cruising alongside the freeway at, say, 70 miles an hour—and there is a rock up within the air on the prime of its path. It is momentarily at relaxation, however you aren’t. Let the court docket take notice: The rock didn’t hit you. You hit the rock. However the impact is identical. Both means, you want a brand new windshield.
Rock and Roll
That’s a believable state of affairs, however what if there isn’t any truck in entrance of you? Truly, a extra widespread explanation for windshield harm is a rock mendacity within the highway that will get kicked up by one other automobile. You would possibly suppose it will get shot again on the automobile behind, however that’s not fairly proper. The rock nonetheless doesn’t transfer backward.
Image this: a wheel is rolling alongside the highway and a rock will get wedged between the tire treads. When the rock is available in contact with the bottom, it’s at relaxation. This is what that may appear to be:
