Category: falling balls

The physics and science of falling balls

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

Lou Bloomfield Leave a comment

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.

If you fire a bullet horizontally and drop an identical bull at the same moment,…

Lou Bloomfield Leave a comment

If you fire a bullet horizontally and drop an identical bull at the same moment, will they both hit the ground at the same time?

Yes. The fired bullet may travel farther, but it will fall just as quickly as the dropped bullet and they’ll hit the ground at the same moment. This effect explains why you must aim above the target when shooting at something far away. The faster the bullet travels to the target, the less it will drop. An arrow travels slowly enough that it will fall a considerable distance en route. You must aim quite high when shooting an arrow.

Why do you feel no acceleration in free fall, even though you are accelerating?

Lou Bloomfield Leave a comment

Why do you feel no acceleration in free fall, even though you are accelerating?

This wonderful question has many answers. The first, and most direct, is that you do feel the acceleration. You feel an upward fictitious force (not a real force at all, but an effect of inertia) that exactly balances your downward weight. The feeling you experiences is “weightlessness.” That’s why your stomach feels so funny. You’re used to having it pulled downward by gravity but the effect of your fall is to make it feel weightless.

If you had an object in an empty sphere with a radius of a few miles, surrounded…

Lou Bloomfield Leave a comment

If you had an object in an empty sphere with a radius of a few miles, surrounded by equally distributed and very concentrated mass, what effects of gravity would the object feel?

As long as the mass isn’t so concentrated that the laws of general relativity become important, the object won’t feel any gravity at all. The forces from opposite sides of the surrounding mass will cancel exactly. For example, if you were at the center of the earth in a large spherical opening, you would be perfectly weightless. The force from the north side of the earth would balance the force from the south side. This effect is quite remarkable and depends on the fact that gravity becomes weaker as the inverse square of the distance separating two objects. That way, even if you aren’t in the exact center of the earth, the forces still cancel.

Why does a ball fall 4.9 meters during its first second of falling?

Lou Bloomfield Leave a comment

Why does a ball fall 4.9 meters during its first second of falling?

As a simple argument for that result, think about the ball’s speed as it falls: it starts from rest and, over the course of 1 second, it acquires a downward speed of 9.8 m/s. Its average speed during that first second is half of 9.8 m/s or 4.9 m/s. And that is just how far the ball falls in that first second: 4.9 m. By holding the ball 4.9 m above the floor, you can arranged for it to hit one second after you drop it.