Question

The school bus slows from 60 km/h to 40 km/h when entering the school zone.

Given that this change of speed occurred over 8 seconds, calculate the average deceleration of the bus.

Answer 1

To calculate the average deceleration of the bus, we can use the following formula:

• Average deceleration = (Final velocity - Initial velocity) / Time taken

Here, the initial velocity (v1) is 60 km/h, the final velocity (v2) is 40 km/h, and the time taken (t) is 8 seconds. To make the units consistent, we'll convert the velocities from km/h to m/s.

• 1 km/h = 1000 m / 3600 s = 5/18 m/s

• v1 = 60 km/h * (5/18) = (60 * 5) / 18 = 50/3 m/s v2 = 40 km/h * (5/18) = (40 * 5) / 18 = 100/9 m/s

Now, we can plug the values into the formula:

• Average deceleration = (v2 - v1) / t Average deceleration = ((100/9) - (50/3)) / 8

Now, we'll find a common denominator for the fractions and simplify:

Average deceleration = ((300 - 450) / 27) / 8 = (-150 / 27) / 8

Lastly, we'll divide the fraction by 8:

Average deceleration = -150 / (27 * 8) = -150 / 216

So, the average deceleration of the bus is approximately -150/216 m/s².