Question

A car accelerates from rest at -3.00m/s^2. What is the velocity at the end of 5.0s? What is the displacement after5.0s?

Answer 1

Speed = (acceleration) x (time)
Velocity = (speed) in (direction of the speed)

Speed = (-3 m/s²) x (5 s) = 15 m/s
Velocity =
             (15 m/s) in the direction opposite to the direction you call positive.

Displacement = (distance between start-point and end-point)
                           in the direction from start-point to end-point.

Distance = (1/2) (acceleration) (time)²
Distance = (1/2) (3 m/s²) (5 s)²
                 = (1/2) (3 m/s²) (25 s²)  =  37.5 meters

Displacement =
                     37.5 meters in the direction opposite to the direction you call positive.