Category: falling balls

The physics and science of falling balls

While gravity supposedly makes all objects accelerate at the same rate, feathers…

Lou Bloomfield Leave a comment

While gravity supposedly makes all objects accelerate at the same rate, feathers do not seem to comply. What factors affect the feather’s acceleration, besides air resistance (which should affect all objects equally)?

Actually, air resistance doesn’t affect all objects equally. The feather has so much surface area that it pushes strongly on the air through which it moves and the air pushes back. For an object with very little mass and weight, the feather experiences an enormous amount of air resistance and has great difficulty moving through the air. That’s why it falls so slowly. If you were to pack a feather into a tiny pellet, it would then fall just about as fast as other objects. Similarly, you fall much more slowly when your parachute is opened because it then interacts with the air much more effectively.

If you drop a penny from the Empire state building – could it really puncture a …

Lou Bloomfield Leave a comment

If you drop a penny from the Empire state building – could it really puncture a hole in a car because of its constant acceleration?

Probably not. If the penny were to fall sideways, so that it had as little air resistance as possible, it would reach about 280 km/h (175 mph). That speed ought to be enough to drive the penny into the car if its top were thin enough. However, studies have shown (see http://www.urbanlegends.com/science/penny_falling_impact.html) that coins tumble as they fall and experience substantial air resistance. As a result, you could probably catch a falling penny in your hand, although it might sting a bit. A falling ballpoint pen, because of its aerodynamic shape, is another matter.

Why do objects on earth accelerate downward at the same speed regardless of thei…

Lou Bloomfield Leave a comment

Why do objects on earth accelerate downward at the same speed regardless of their mass?

What you mean here is that they accelerate downward at the same rate (“speed” has a particular meaning that isn’t so well suited to discussions of acceleration). This fact comes about because, although massive objects are harder to accelerate, they also experience more weight. Thus a huge stone will fall at the same rate as a small rock because the stone will be pulled downward more strongly by gravity and that extra pull will make up for the stone’s greater inertia.

If you dropped a bullet and at the same time, fired a bullet directly at the gro…

Lou Bloomfield Leave a comment

If you dropped a bullet and at the same time, fired a bullet directly at the ground, wouldn’t the bullet fired at the ground hit the ground first?

Sure it would. The fired bullet will only hit the ground at the same time as the dropped bullet if the fired bullet is shot exactly horizontally. If you fire the bullet at the ground, then it starts out with an enormous downward component to its velocity. The falling bullet doesn’t have this initial downward component to its velocity and never catches up.

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.