Answer: 15m/s
Explanation: <u>Average</u> <u>Velocity</u> is vector describing the total displacement of an object and the time taken to change its position. It is represented as:
At t₁ = 1.0s, displacement x₁ is:
x(1) = 28
At t₂ = 4.0s:
x(4) = 73
Then, average speed is
v = 15
The average velocity of a car between t₁ = 1s and t₂ = 4s is 15m/s