It's Dynamic! Force and Energy
||edHelper's suggested reading level:
||grades 5 to 7
||Flesch-Kincaid grade level:
||dynamics, kinetic, measurable, reemerge, acceleration, velocity, relation, convert, withstand, steeper, electrical, unit, affected, design, therefore, mass
||Sir Isaac Newton
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It's Dynamic! Force and Energy
By Trista L. Pollard
1 According to Sir Isaac Newton, bodies at rest will remain at rest, and bodies in motion will remain in motion. However, in the science of dynamics, force and energy are important factors that can affect the motion of bodies. Force is the push or pull of an object that tends to produce acceleration of the body's motion in the direction of the force. Force also changes the size and shape of a body. There are four basic forces in nature. However, in relation to machines and vehicles, we will only talk about the forces related to gravity and motion. Gravity is the force of attraction between any two objects. This force depends on the mass or weight of each object and their distance from each other. Gravitational force is always attractive; however, over increasing distances, the force decreases, but it is still measurable. Gravity is the force that keeps all beings and objects on earth. If we traveled into space, we would experience an environment that has zero gravitational pull. Another concept related to gravity is free fall. Free fall occurs when objects fall downward toward earth due to earth's gravitational pull. If two different objects with different masses were in a free fall from the same height, they would have the same acceleration regardless of their masses. I wonder if a free falling feather and a bowling ball would reach the ground at the same time. I don't recommend trying this experiment; I was just wondering.
2 Momentum is the force or speed of movement. This occurs when force is applied to an already moving object. Once the force is applied, the object's momentum may increase or decrease. When force is not applied to a moving body, its momentum will not change. Think about water flowing down a steep hill. As the water flows down the hill, it gains momentum to the point where its velocity or speed will increase. When your little brother goes running across the grass and tries to run up the hill to the playground, you will notice his momentum decrease as the hill becomes steeper. As he runs toward the top, his velocity will decrease, and he will probably be tired once he gets to the playground.
3 There are other forces that affect the movement of objects. Friction is a force that resists the movement between two objects that are touching. Increasing the friction on a moving object will decrease the object's velocity. An example would be when you go "skating" in your socks on your kitchen floor. Since there is very little friction, you should move rather quickly. However, as soon as you try to continue your sock skating on the rug, you will notice that your motion almost comes to a halt. The friction between your socks and the rug is greater than the friction was between your socks and the smooth kitchen floor. Therefore, your motion has decreased. Tension is another type of force that involves objects like springs. Tension is the force that is exerted or produced by a stretched object. The tighter the object is pulled, the greater the tension. Sometimes the tension becomes too great causing the object to break. Springs, due to their design, are able to withstand huge amounts of tension. It is for this reason they are used as parts of machines and other objects. Now that we have talked about force, we will talk about energy.
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