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This one is a great and common question. 

If you just want the answer without explanation skip to the bottom and you will get it. 

This is the theory of conservation of energy. That means that energy cannot be created or destroyed; so all of the energy in the universe was here at the beginning is the same energy that is here now. Therefore we now have to see in this question how energy was changed from one type to another or how it was ‘transferred’ from one to another. 

There are a few key words when we are talking about energy. When we talk about “height” and “energy” together we are almost always talking about gravitational potential energy or GPE for short. The equation for this is:

                   GPE = mass x gravitational acceleration x height 

                   GPE = mgh 

If we substitute the numbers into the equation and calculate the energy we get:


                     GPE = m x 9.81 x 2
                     GPE = 19.62m

We do not know the mass of the car but it’s okay at this point. 



The second part of the question indicates that we are looking for the speed or velocity AND energy. This type of energy is called kinetic energy. Any thing that moves has kinetic energy. 

                 KE = 1/2 mv^2

To show that all energy has been transferred we have to make both equations equal to each other. 


              KE = GPE
          1/2mv^2 = mgh
          1/2mv^2 = 19.62m

1. Divide by m.

           1/2v^2 19.62

2. Divide by 1/2.

             v^2 = 39.24

3. Square root both sides.

             v  = 6.264m/s

Physics

A toy car slides down a slope. If the top of the slope is 2m higher than the foot of the slope, how fast will the car be moving when it reaches the foot? (Assume that all of its g.p.e is transformed to k.e

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