A bus slams on its breaks and goes from 30 km/hr to 15km/hr in 4 seconds. What is its acceleration?

1 answer:

5 0

Acceleration = (change in speed) / (time for the change).

Change in speed = (15 - 30) = -15 km/hr
Time for the change = 4 sec

Acceleration = (-15 km/hr) / (4 sec) = -3.75 km/hr per second .

Is that a lot ? Not much ?

Let's convert it to a unit that we can think about:

(-15 km/hr) x (1,000 m/km) x (1 hr / 3,600 sec) =

(-15 x 1,000) / (3,600) = -(4 and 1/6) m/sec .

So the acceleration of the bus is -(4 and 1/6) m/sec² .

The negative sign means that it slowed down.

(4 and 1/6) m/sec² is about 42% of the acceleration of gravity ...
the acceleration the bus would have if it drove off of a cliff.

When the car or the bus you're riding in slows down at that rate,
you feel 42% of your weight pulling you forward against your
seat belt. That's quite a drastic acceleration !

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To solve this problem, we must know the gravitational force of the planet. The equation would be,

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