Why do some objects bounce off the ground (balls) whereas others would break (eg…

Why do some objects bounce off the ground (balls) whereas others would break (eggs)?

Some objects can deform elastically, storing energy in the process, while others can’t. The surface of a rubber ball is made up of long, flexible molecules called polymers that can bend and stretch without breaking. As the ball’s surface dents during an impact, these polymer molecules move about and begin to exert forces on one another (storing energy in the process). As the ball rebounds, these molecules release their stored energy and push the ball back into the air. An egg, on the other hand, is made of hard, crystalline material that shatters during the deformation. Whole rows of atoms and molecules rip apart from one another and are unable to return. The egg doesn’t store the impact energy. Instead, it turns that energy into thermal energy. The shell just crumbles.

Why does a basketball bounce higher than a bowling ball?

Why does a basketball bounce higher than a bowling ball?

When a ball bounces from a rigid surface, the ball’s surface distorts inward and then pops back outward. During the inward motion, the ball stores energy—pushing its surface inward takes energy. During the outward motion, the ball releases that stored energy. But not all the energy invested in the ball emerges as useful work. Some of that energy is turned into thermal energy and never reappears. A properly inflated basketball returns a good fraction of the energy it receives while other balls may not. In fact, a bowling ball bounces pretty well from a hard surface such as cement. But when it hits a softer surface such as wood, the wood receives much of its energy and wastes that energy as thermal energy.

Why does a rubber ball transfer more forward momentum as the ball rebounds off a…

Why does a rubber ball transfer more forward momentum as the ball rebounds off an object?

As the ball hits a wall and stops, it transfers its forward momentum to the wall. The ball pushes the wall forward for a certain time and thus provides a forward impulse to the wall. As the ball rebounds from the wall, it also pushes the wall forward for a certain time and thus provides an additional forward impulse to the wall. The ball ends up traveling in the opposite direction from that which it had initially, so its momentum points in the opposite direction. This reversal of momentum required an enormous transfer of forward momentum to the wall; so large that the ball actually ended up with a negative amount of forward momentum (which is equivalent to a positive amount of backward momentum).

Why when you play baseball is it easier to hit a home run off a fast ball than o…

Why when you play baseball is it easier to hit a home run off a fast ball than off a slow ball?

The speed of the ball’s rebound from the stationary bat (let’s adopt the bat’s inertial frame of reference for the moment) depends on the speed at which the ball and bat approach one another. The faster the ball approaches the bat, the higher the ball’s rebound speed will be. Since a fastball approaches the bat faster than a slow ball, the fastball also leaves the bat at a higher speed and is more likely to fly out of the outfield for a home run. You can even consider the case in which the batter tries to bunt and holds the bat stationary. A fastball will approach the bat faster and will bounce back faster than a slow ball will. If the pitch is fast enough, the rebounding ball could conceivably fly past the outfield for a home run, too.

How do rubber bouncing balls work? Does the table exert more force than is appli…

How do rubber bouncing balls work? Does the table exert more force than is applied, causing an upward acceleration?

The table never pushes up on the ball harder than the ball pushes down on the table. That would violate Newton’s third law and is just not the way our universe works. As the ball strikes the table, the two objects dent. The ball dents most and has work done on its surface—the table pushes the surface inward and work is force times distance in the direction of that force. The ball stores this work/energy as a deformation of its elastic surface and a compression of the air inside the ball. The ball then rebounds from the table as this stored energy reemerges as kinetic energy in the ball. Throughout the bounce, the upward force that the table exerts on the ball is much larger than the ball’s downward weight. As a result, the ball accelerates upward the whole time. It starts the bounce heading downward and finishes the bounce heading upward.

Would a baseball bat do more damage on a person if the point of contact was the …

Would a baseball bat do more damage on a person if the point of contact was the very end of the bat (torque=force x lever arm) or at the sweet spot? (assuming the bat was swung with a constant angular momentum)

The sweet spot. Hitting someone with the bat is very similar to hitting a ball. When you hit a ball with the sweet spot of the bat, the bat slows down and begins to rotate slowly. The slowing is good because it means that some of its kinetic energy has been transferred to the ball. The rotation is bad, because it means that the bat has put energy into rotation (spinning objects have kinetic energy). If the ball hit the bat’s center of mass, the bat wouldn’t rotate and the transfer of energy would be better; except for one new problem: the bat would begin to vibrate and that vibration would use energy. By hitting the ball on the sweet spot, you keep the bat from vibrating and wasting some of its energy. The transfer of energy and momentum to the ball is maximized. The same occurs when hitting any other object, including a person.

If all the laws of physics always happen the same, then what relevance does the …

If all the laws of physics always happen the same, then what relevance does the frame of reference have?

If you observe the world from an inertia frame of reference—meaning that you aren’t accelerating—then all of the laws of physics will apply properly to the objects you see. Energy will be conserved during activities, momentum will be transferred between objects without being created or destroyed, and so on. So it’s true that any inertial frame of reference will do. However, there is often a “best” reference frame from which to observe a situation. A good example of this is the situation in which a ball bounces from a bat. The best inertial reference frame from which to watch that bounce is the frame of the moving bat. In that special inertial reference frame, the bat doesn’t move and the ball bounces off the stationary bat.

If I’m a WWF Wrestler, and I sling-shot myself off the ropes, and my momentum ca…

If I’m a WWF Wrestler, and I sling-shot myself off the ropes, and my momentum carries me as I put a flying shoulder block on my opponent, is my momentum conserved and do I feel any momentum against me?

As you bounce off the ropes, you exchange momentum with the ropes (and the earth). As a result, you normally reverse your momentum and head back into the ring. When you hit your opponent, you begin to exchange momentum with him/her. If you hit your opponent feet first and jump backward, you will reverse your direction of travel again and your opponent will receive an enormous amount of forward momentum. All of this transfer of momentum means that your personal momentum will change often but the total momentum of the earth and its population won’t change. That momentum will just be rearranged amount the various objects.