# I Classical Mechanics Goldstein Eq3.14 help please

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1. Dec 7, 2017

### bengeof

how is md^2r/dt^2 . dr/dt = d/dt (1/2 m (dr/dt)^2 )

Thank You

2. Dec 7, 2017

Chain rule.

3. Dec 7, 2017

### bengeof

Can you work it out for me explicitly ?

4. Dec 7, 2017

### Ibix

Can you state the chain rule? Can you apply it to the time derivative of $(dr/dt)^2$?

5. Dec 7, 2017

6. Dec 7, 2017

### bengeof

2dr/dt . . is that right ?

7. Dec 7, 2017

8. Dec 7, 2017

### PeroK

That makes no sense. The LHS is the answer to the derivative on the RHS. There's nothing to work out on the left.

The stackexchange link I gave you is all about why that is not the answer!

9. Dec 7, 2017

### bengeof

okay Got it. Thank you so much !!

10. Dec 8, 2017

### Dr.D

The rest of Goldstein may present difficulties.