0633 Kinetic Energy Solution

0:00  0:04Now, you could have solve this problem using the equation of motion that we learned about in unit 2

0:04  0:08or you could have use our new super cool technique of the work energy theory,

0:08  0:10which is how I'm going to solve this one.

0:10  0:13For work energy theory, first we need the total work and that is given by this equation.

0:13  0:15Well, let's look at the forces on the ball.

0:15  0:17Well, this is an easy one, there is only gravity pointing downwards.

0:17  0:22Okay, and Δx, well, we're just going to use this distance 57 meters.

0:22  0:28W = mg * 57 and that is also equal to the change in kinetic energy.

0:28  0:33And notice that an amazing but necessary thing happens, the mass cancels out.

0:33  0:35I can also multiply both sides by 2.

0:35  0:39Oh and don't forget that the initial velocity was zero since it was released from rest,

0:39  0:41and now, we have this equation.

0:41  0:46I just take the square root of both sides, and I get the final velocity of 34 m/s.

0:46  0:48So, now, we have another tool to solve this problem.

0:48  0:54We'll find there's actually places where this tool will solve problems that our previous tools couldn't.

0:54  0:56I think I teased you a little too much when I said,

0:56  0:59I don't know what energy is, but I know what energy does.

0:59 Let's dove into that a little more deeply.
 Title:
 0633 Kinetic Energy Solution
 Description:

All units in this course below:
Unit 1: http://www.youtube.com/playlist?list=PLF79FCD2E20F4F9FC
Unit 2: http://www.youtube.com/playlist?list=PL0E63503E8232BB23
Unit 3: http://www.youtube.com/playlist?list=PL9BF147060D26ADF6
Unit 4: http://www.youtube.com/playlist?list=PLDB3B73A8BCD831C3Join the class at http://www.udacity.com to gain access to interactive quizzes, homework, programming assignments and a helpful community.
 Team:
 Udacity
 Project:
 PH100  Intro to Physics
 Duration:
 01:02
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