Kinematics Basics: Solving a & b with a=-8m/sec2

[adoado]

Homework Statement

The acceleration of a particle is defined by a = -8 m/sec². Knowing that x = 20 when t = 4 and x = 4 when v = 16, determine:

• The time when the velocity is zero
• The velocity and the total distance traveled when t = 11

Homework Equations

The Attempt at a Solution

I think once I get part 'a' I can do part 'b'. Here is my attempt:

a = -8m/sec²
So
V = -8t + C.

How can I get C? Do I need to use another representation of acceleration? I am not sure where to go.

Any advice greatly appreciated!
Adrian

 

[CompuChip]

C is the velocity at time t = 0.
I would suggest using the formula
s(t) = (1/2) a t² + C t + D (*)
where C is the velocity v(0) at time t = 0 and D is the displacement s(0) at t = 0.

If you plug in the two given points you can determine C and D. Then you can use both formula (note that v(t) = -8t + C will actually be the derivative of formula (*) above).