During the dive, inertia is constantly varying between 6. As the angular velocity increases, moment of inertia decreases and vice versa hence keeping angular momentum constant throughout the dive. In the final phase, the inertia initially decreases but as the divers straightens up; preparing to enter the water the moment of inertia begins to rise.
Graph 2 shows the moment of inertia for the backward pike dive. The graph is again divided into the 3 different phases. Initially, in phase 1, the moment of inertia is Once the diver has left the board, the moment of inertia decreases and continues to decrease until the diver assumes the pike position at the end of phase 1. During the second phase, the moment of inertia fluctuates in accordance with the decreasing angular velocity, keeping angular momentum constant.
At frame , the diver is starting to prepare for his entry into water and thus begins to release from the pike position. As he does so, the moment of inertia increases and continues to increase as the diver stretches out fully in order to enter the water in a straight line.
Graph 3 shows a comparison between the moments of inertia for both the forward and backward pike dives. The dives were compared from the frame of last contact with the board until the diver enters the water. The moment of inertia for the forward pike is more variable throughout the dive, yet both dives still follow a similar pattern.
As the diver leaves the board moment of inertia decreases for both dives. The backward pike dive takes a bit longer to decrease fully due it taking slightly longer to reach the pike position during a backward dive. However, the backward pike dive decreases to a lower moment of inertia meaning that the angular velocity is greater and that the diver is in a tighter pike position during the backward pike. At the end of the dive, inertia increases as the angular velocity decreases.
The backward pike dive has a greater increase in the inertia due to the decrease in the angular velocity. As the forward pike dive had a slower angular velocity, there is less of an increase in inertia as the diver enters the water. Conclusion Moment of inertia is a calculation of the required force to rotate an object. The value can be manipulated to either increase or decrease the inertia. Friction is an external force.
Experiments have thoroughly verified that any change in velocity speed or direction must be caused by an external force. The idea of generally applicable or universal laws is important not only here—it is a basic feature of all laws of physics. Identifying these laws is like recognizing patterns in nature from which further patterns can be discovered. The property of a body to remain at rest or to remain in motion with constant velocity is called inertia. As we know from experience, some objects have more inertia than others.
It is obviously more difficult to change the motion of a large boulder than that of a basketball, for example. The inertia of an object is measured by its mass. The quantity or amount of matter in an object is determined by the numbers of atoms and molecules of various types it contains.
Unlike weight, mass does not vary with location. The mass of an object is the same on Earth, in orbit, or on the surface of the Moon. In practice, it is very difficult to count and identify all of the atoms and molecules in an object, so masses are not often determined in this manner. Operationally, the masses of objects are determined by comparison with the standard kilogram. Supposing you were in space in a weightless environment , would it require a force to set an object in motion?
Even in space objects have mass. And if they have mass, they have inertia. That is, an object in space resists changes in its state of motion. A force must be applied to set a stationary object in motion. Newton's laws rule - everywhere! Fred spends most Sunday afternoons at rest on the sofa, watching pro football games and consuming large quantities of food.
What affect if any does this practice have upon his inertia? Fred will increase his mass if he makes a habit of this. And if his mass increases, then his inertia increases. Ben Tooclose is being chased through the woods by a bull moose that he was attempting to photograph.
The enormous mass of the bull moose is extremely intimidating. Yet, if Ben makes a zigzag pattern through the woods, he will be able to use the large mass of the moose to his own advantage.
Explain this in terms of inertia and Newton's first law of motion. The large mass of the bull moose means that the bull moose has a large inertia. Thus, Ben can more easily change his own state of motion make quick changes in direction while the moose has extreme difficulty changing its state of motion. Physics for better living! Two bricks are resting on edge of the lab table. Shirley Sheshort stands on her toes and spots the two bricks. She acquires an intense desire to know which of the two bricks are most massive.
Since Shirley is vertically challenged, she is unable to reach high enough and lift the bricks; she can however reach high enough to give the bricks a push. Discuss how the process of pushing the bricks will allow Shirley to determine which of the two bricks is most massive. What difference will Shirley observe and how can this observation lead to the necessary conclusion? The bricks, like any object, possess inertia. That is, the bricks will resist changes in their state of motion.
If Shirley gives them a push, then the bricks will offer resistance to this push. The one with the most mass will be the one with the most inertia. This will be the brick which offers the most resistance. This very method of detecting the mass of an object can be used on Earth as well as in locations where gravitational forces are negligible for bricks.
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