02. Define the following terms:
(1) Elastic force
(2) Soil
(3) Marble
(4) Energy
(5) Gravitational force
hanem
Answers
Answer: We already know something about gravity from our study of free-fall and projectile motion. We know that the acceleration is the same for objects of different masses. While we have used this as a model, it is a big step to claim that gravity fundamentally follows this rule. We know that a feather will experience the same acceleration due to gravity as a stone if air resistance is removed. Now how do we put air resistance back into our model so that the reduced acceleration of the feather makes sense?
The effect of reduced acceleration is easy to show with an FBD of two objects that are identical except for mass and are falling through the air at the same speed. For these two objects, the air resistance forces are equal, and the gravity force is greater on the heavier object. The net forces on the two objects are therefore different, giving the following accelerations:
a(heavy)=Fgravity(heavy)−Fairm(heavy)a(light)=Fgravity(light)−Fairm(light)g=Fgravitym⎫⎭⎬⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⎪⇒a(heavy)=g−Fairm(heavy)a(light)=g−Fairm(light)(2.3.1)
So the reason the heavier mass accelerates more is simply that the effect that the air resistance force has on it is smaller. Care must be taken not to draw quick conclusions, because it is possible to draw an incorrect conclusion about a single force by not paying attention to a second force that is present. One simple result comes out of the free-fall case without air resistance:
Fgravity=ma, a=g ⇒Fgravity=mg(2.3.2)
Alert
It is important to understand that here g has a different meaning than it had when we were discussing motion involving gravity-caused acceleration. Here the g is a physical constant, which we use to determine the gravity force on an object with mass m . It does not mean that the object is accelerating at 9.8ms2 ! When an object experiences no other force than gravity, the object's acceleration just happens to equal this constant, but the constant is the present regardless of the state of acceleration of the object.
Tension
When we model problems that involve tension forces exerted by strings or ropes, we usually assume that the string or rope has no mass. Not to do so brings in some challenging (but interesting!) complications that are generally not the focus of that problem. For example, imagine two people having a tug-o-war, where one person is winning, and is therefore accelerating the other. A FBD of just the rope shows two forces on it (if we ignore gravity), one in each direction. With one of the people winning, not only do both people accelerate, the rope does as well. This means that there is a net force on the rope, and therefore one person is pulling on the rope harder than the other person.
By assuming that the rope is massless, the mass-times-acceleration for the rope is just zero, which means there is no net force on it, despite the fact that it is accelerating. With no net force on it, the two combatants are pulling on it with equal force, which means that essentially the force one person exerts on it is transmitted through the rope to act on the other person. That is, the rope becomes no different than a case of the two people clasping hands and pulling on each other. This allows us to use ropes as an idealized means of allowing the “by” object to exert a force “on” another object from a distance. Without this device, we would either have to devise examples in an awkward manner, or overly-complicate problems by including accelerating massive ropes.
Alert
Occasionally ropes will be used as a conduit for expressing third-law pairs (“tension force on A by B,” where neither A nor B is the rope), but this is dangerous, because ropes can also transmit the force around a pulley, in which case the Newton's third law pair of forces are clearly not in opposite directions.
Pulleys are another aspect of tension we should say a word about. If a pulley experiences friction as it rotates, or has some mass (so that its rotation requires the acceleration of some mass), then the tension force is not transmitted around it unaffected. We will actually look at the case of pulleys with mass later in the course, but for now we idealize them as we do ropes – no friction and no mass.
Answer:
1) Elastic Force. The elastic force occurs as a deformed object (think spring) tries to return to its original shape. The force always acts in a direction that will return it to its original shape. Hooke's Law describes how many objects will produce a greater force in direct proportion to the amount of deformation.
2) Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth' s body of soil, called the pedosphere
3) Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated, although there are exceptions. In geology, the term marble refers to metamorphosed limestone, but its use in stonemasonry more broadly encompasses unmetamorphosed limestone
4) the ability to be very active or do a lot of work without getting tired
5) Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides
Explanation: