# Homework Help: Prove in case of projectile d^2 (v^2 ) / dt^2 = 2g^2

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1. Aug 2, 2015

### Safi Majid

1. The problem statement, all variables and given/known data
for a projectile show that d^2 (v^2) / dt^2 = 2g^2

2. The attempt at a solution
=d/dt (d(v^2)/dt)
=d/dt (2v)

2. Aug 2, 2015

### Orodruin

Staff Emeritus
Your attempt is using a very strange notation. Please write out the details using standard notation and explain what you are doing in each step.

3. Aug 2, 2015

### ehild

Welcome to PF!
The velocity v depends on t. You need to apply the Chain Rule to get the time derivative of v2.

4. Aug 2, 2015

### Safi Majid

i have used second derivative on it

5. Aug 2, 2015

### Safi Majid

In standard notation it is
d2(v2)/dt2=2g2

6. Aug 2, 2015

### HallsofIvy

That was not what was being questioned. The derivative of $v^2$, with respect to t, is NOT "2v". It is $2v\frac{dv}{dt}$.