U = 60km/hr × 5/18 = 50/3 m/sec
v = 0
t = 20s
a = ?
we know that-
a = v-u/t
a = -50/3 /20
a = -50/60
∴ a = -0.83m/sec²
negative sign shows that it is a retarded motion.
so its acceleration is 0.83 m/sec²..

Calculating Acceleration of the Bus

To calculate the acceleration of the bus, we need to use the formula:

Acceleration = (Final Velocity - Initial Velocity) / Time Taken

Here, the initial velocity is 60 kps (kilometers per second) since that is the velocity at which the bus is moving before the brakes are applied. The final velocity is 0 kps since the bus comes to a complete stop. The time taken is 20 seconds.

Substituting these values into the formula, we get:

Acceleration = (0 kps - 60 kps) / 20 s

Acceleration = -3 kps^2

Explaining the Calculation

The negative sign in the answer indicates that the acceleration is in the opposite direction to the initial velocity of the bus. This is because the brakes are being applied to slow down the bus, so the acceleration is acting in the opposite direction to the motion of the bus.

The unit of acceleration is kilometers per second squared (kps^2). This means that for every second the bus is slowing down by 3 kilometers per second.

Conclusion

In conclusion, the acceleration of the bus when the brakes are applied is -3 kps^2. This value tells us how quickly the bus is slowing down and in which direction. It is important to note that the braking distance of the bus will depend on several other factors such as the condition of the brakes, the weight of the bus, and the friction between the tires and the road.