Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K. If the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of kilograms-meters squared per second squared.
Calculate the kinetic energy in Joules possessed by each of the following objects. Remember to use the correct number of significant figures in your answer. A 71 kg man walking at 1. A 71 kg man running at 5. A kg car 2 tons travelling at J Correct!
Life is impossible without the enrgy. Sun is the biggest natural source of free energy. An object that possesses energy can exert a force on another object and energy is transferred from the former to the latter. The second object move as it receives energy and therefore do some work.
This implies that any object that possesses energy can do work. Activities like riding horse, driving car, rolling stone, flying plane are the examples of kinetic energy. The kinetic energy of an object increases with its speed. Consider an object of mass m moving with a uniform velocity u. Let is now be displaced through a distance s when a constant force F acts on it in the direction of its displacement. Potential energy: The potential energy possessed by the object is the energy present in it by virtue of its position or configuration that means potential energy is stored energy in the object when work is done on the object but there is no change in the velocity or speed of the object.
Gravitational potential energy is the energy possess by the object when it is raised against the gravity. It is defined as the work done in raising it from the ground to that point against gravity. This reveals another general truth.
When friction is negligible, the speed of a falling body depends only on its initial speed and height, and not on its mass or the path taken. For example, the roller coaster will have the same final speed whether it falls Third, and perhaps unexpectedly, the final speed in part 2 is greater than in part 1, but by far less than 5.
Finally, note that speed can be found at any height along the way by simply using the appropriate value of h at the point of interest. We have seen that work done by or against the gravitational force depends only on the starting and ending points, and not on the path between, allowing us to define the simplifying concept of gravitational potential energy.
We can do the same thing for a few other forces, and we will see that this leads to a formal definition of the law of conservation of energy.
One can study the conversion of gravitational potential energy into kinetic energy in this experiment. On a smooth, level surface, use a ruler of the kind that has a groove running along its length and a book to make an incline see Figure 5.
Place a marble at the cm position on the ruler and let it roll down the ruler. When it hits the level surface, measure the time it takes to roll one meter. Now place the marble at the cm and the cm positions and again measure the times it takes to roll 1 m on the level surface.
Find the velocity of the marble on the level surface for all three positions. Plot velocity squared versus the distance traveled by the marble. What is the shape of each plot?
Figure 5. A marble rolls down a ruler, and its speed on the level surface is measured. Figure 6. Hydroelectric facility credit: Denis Belevich, Wikimedia Commons. Figure 7. A toy car moves up a sloped track. That is, the energy stored in the lake is approximately half that in a 9-megaton fusion bomb. Skip to main content. Work, Energy, and Energy Resources. Search for:. Gravitational Potential Energy Learning Objectives By the end of this section, you will be able to: Explain gravitational potential energy in terms of work done against gravity.
Show how knowledge of the potential energy as a function of position can be used to simplify calculations and explain physical phenomena.
Example 1. The Force to Stop Falling A Example 2. Finding the Speed of a Roller Coaster from its Height What is the final speed of the roller coaster shown in Figure 4 if it starts from rest at the top of the
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