To find the initial speed of the car before it accelerated, we can use the equation of motion:
v = u + at
where:
v = final velocity = 90 m/s
u = initial velocity (unknown)
a = acceleration = 3 m/s^2
t = time taken for acceleration = 10 seconds
Rearranging the equation to solve for u:
u = v - at
Substituting the given values:
u = 90 m/s - (3 m/s^2)(10 s)
u = 90 m/s - 30 m/s
u = 60 m/s
Therefore, the car was going 60 m/s before it accelerated.