Over a span of 6.0 seconds, a car changes it's speed from 89 km/h to 37 km/h. What is its average acceleration in meters per second squared?

a. 2.4

b. - 8.7

c. - 2.4

d. - 6.2

Acceleration = (change in speed) / (time for the change)

change in speed = (speed at the end) - (speed at the beginning)

change in speed = (37 km/hr) - (89 km/hr) = - 52 km/hr

Acceleration = (-52 km/hr) / (6 sec)

Acceleration = (-26/3) km / (hr·sec)

Units: (1/hr·sec) · (hr/3600 sec) = 1 / 3600 sec²

(-26/3) km / (hr·sec) = (-26/3) km / (3600 sec²)

= - 26,000 / (3 · 3600) m/s²

Acceleration = - 2.41 m/s²