Question

A car travels in a straight line for 4.4 h at a constant speed of 81 km/h. What is its acceleration?

Answer 1

The speed and length of time don't matter.

Constant speed in a straight line is the DEFINITION of ZERO acceleration.

Answer 2

Answer:

$a = 0m/s^2$

Explanation:

we can use the equation:

$v_f = a(t) + v_i$

And plug in our numbers:

$81km/h = am/s^2(4.4h) + 81hm/h$

$0 = am/s^2(4.4h)$

$0 = am/s^2$

$a = 0m/s^2$

Because the speed was constant, there was no difference between the final and initial velocities, meaning that once you do the math you see there is no acceleration affecting the speed.