A car's speedometer reads 20 m/s after accelerating, from a standing start, for 25s. What was the magnitude of its acceleration?

Magnitude of acceleration = (change in speed) / (time for the change)

Change in speed = (speed at the end) - (speed at the beginning)

= (20 m/s) - zero

= 20 m/s

Time for the change = 25 s

Magnitude of acceleration = (20 m/s) / (25 sec)

= (20/25) m/s²

= 0.8 m/s²