# Homework Help: Nonuniform Linear Acceleration

1. Jul 10, 2016

### Auburn2017

1. The problem statement, all variables and given/known data
Refer to figure.

2. Relevant equations
v=ds/dt → ds=vdt

3. The attempt at a solution
I tried taking the derivative of the given position function. Then I am kind of lost from there.

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2. Jul 10, 2016

### Hamal_Arietis

First, you must find velocity equation: v=ds/dt=f(t)
After that v=40m/s then f(t)=v=> t0
Finally, find aceleraition equation: a=dv/dt =g(t)
Replace the t0 a(t0)=g(t0)

3. Jul 10, 2016

### Auburn2017

If you do this then you don't get the solution that was provided...

4. Jul 10, 2016

### Hamal_Arietis

Ah two time are different. It is the time that you find aceleration
Find the time from v=15 to v=75
From v(t) equation: f(t1)=15m/s => t1
f(t2)=75m/s => t2 So the time is t2-t1

5. Jul 10, 2016

### cnh1995

If initial velocity is the velocity at t=0, it is not 15m/s. If you neglect the 15m/s, your answers will match the given answers.

6. Jul 11, 2016

### haruspex

Seems to me you get the given answers by taking the initial speed as 15m/s and changing the displacement to be 3t3+15t+6 to match.

7. Jul 11, 2016

### cnh1995

Right.. I meant to say neglect 14m/s and take initial velocity as 15m/s. I was about to edit but my network went off and later when I signed up again, I totally forgot that I was going to edit the post. Thanks!