Kinetic Energy

First Definition for Kinetic Energy

When something is in motion it is said to have kinetic energy.

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Here's the code that runs the above animation.

You can change the code, if you like, and then click the following 'Reevaluate code' button. The program will then work as per your changes. Of course, your changes, especially random changes, can introduce errors, miscalculations, and browser crashes. If you need to get things back to their original condition, just reload this page using your browser's reload button.

The intention here is to conveniently show the inner workings of this program so that you understand how the diagram is drawn. Can you figure out how to change this code so that the object moves faster?

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// kinetic energy, moving object

window.loopWait = 50; // ms.

window.objectDiv;

window.xMin; // left pixel bound
window.xMax; // right pixel bound
window.x;    // current pixel position
window.dx;   // delta position


window.setup = function()
{
	// get the animated DOM element
	objectDiv = jQuery('#objectDivId');
	
	// setup the bounds
	xMin = -60;
	xMax = 660;
	
	// initialize the starting position
	x = xMin;
	
	// set the change in position
	dx = 1;
	
	// position animated DOM element
	objectDiv.css('left', x.toString() + 'px');
};


window.loop = function()
{
	// do math for new position
	update();
	
	// draw object at new position
	render();

	// wait a bit, do it again
	loopTimeout = setTimeout(loop, 50);	
};


window.update = function()
{
	// move down the x-axis
	x += dx;
	
	// if beyound right bound, go back to start
	if(x > xMax) x = xMin;
};


window.render = function()
{
	// place the DOM element at its new position
	objectDiv.css('left', x.toString() + 'px');
};

Formula for Kinetic Energy

For an object that is moving the kinetic energy equals one half times the mass of the object times the square of the speed of the object. In symbols:

E_K = (1/2)mv²

Example Calculation for Kinetic Energy

How much kinetic energy does an object have if its mass is 5.0 kg and it is moving at a speed of 4.0 m/s?

E_K= (1/2)mv²	Formula for kinetic energy.
E_K= (1/2)(5.0 kg)(4.0 m/s)²	Plug in values for mass, 5.0 kg, and speed, 4.0 m/s.
E_K= 40 J	Kinetic Energy equals 40 J.

Here are some problems to try using the above equation: