If the initial velocity is zero, what is the velocity at t = 6 seconds? If the initial velocity is 20ft /sec what is the velocity at t=6 sec and t=7 sec.

Question

In the acceleration graph a (0)=0 , a (6)=0 , and a (7)= -5 ft /sec^2. How do I do this? Thanks.

Answer 1

I think this has the look of a free fall scenario when the initial velocity is zero.  After 6 seconds the velocity of a freefalling object accelerates at approximately 10 m/s².  So 10 after 1 second, 20 after 2 seconds,...60m/s² after 6 seconds.

 

Now if you have your coordinate system where down is negative than after 6 seconds the object would be falling at -60 (assuming no air resistance is OK if its a freefall problem)

 

I think the other part where the V_initial or V₀ is 20ft/sec then you are dealing with an object that was thrown upward with an initial positive velocity at time t=0.  Acceleration due to gravity (g)  is -32 ft/s² or approx -10m/s^2. depending on the units you are using.

 

a(t)=v₀t + 1/2(g)t²

 

Not sure why you would get a(0)=0 and a(6)=0.  That doesn't sound right.  However you could have 

a(t)=-5=0t + 1/2(-32)t² and then solve for t