6) if a car goes from 20 miles per hour to 10 miles per hour in 5 seconds, find its acceleration.
a.2 miles per hour per second
b.5 miles per hour per second
c.-2 miles per hour per second
d.10 miles per hour per second

Answer;

C.-2 miles per hour per second

Explanation;

Acceleration = change in velocity / time

Acceleration = (final velocity - initial velocity )/time  

Acceleration = (v - u)/t  

Given: u = 20 miles per hour, v = 10 miles per hour  

t = 5 seconds  

Acceleration = (10 - 20)/5  

Acceleration = -10/5  

Acceleration = -2 miles per hour per second  

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.