To find the acceleration, we can use the equation:
acceleration = (final velocity - initial velocity) / time
In this case, the initial velocity is 72 km/h, and the final velocity is 0 km/h (since the car instantly stops). The time taken to stop is 5 seconds. However, we need to convert the velocities from km/h to m/s to ensure consistent units.
1 km/h is equal to 1/3.6 m/s, so:
Initial velocity = 72 km/h × (1/3.6 m/s) = 20 m/s Final velocity = 0 km/h × (1/3.6 m/s) = 0 m/s
Now, we can substitute the values into the formula:
acceleration = (0 m/s - 20 m/s) / 5 s = -20 m/s²
The negative sign indicates that the car is decelerating or slowing down. Therefore, the acceleration of the car is -20 m/s².