Question

An ice skater slides in a straight line across the ice. As she passes a certain point, her velocity is 24 km/hr. Two seconds later it is 13 km/hr. What is the acceleration of the skater?
5.5 km/hr/sec
-5.5 km/hr/sec
11 km/hr/sec
-11 km/hr/sec

Answer 1

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

Change in speed = (later speed) - (earlier speed) = (13 - 24) = -11 km/hr
Time for the change = 2 seconds

Acceleration = (-11 km/hr) / (2 sec)

Acceleration = -5.5 km/hr-sec  (B)