For 5 seconds, the body speed decreased from 36 km / h to 27 km / h. Find the acceleration of the body.

Given:
t = 5 seconds – time interval;
u1 = 36 kilometers per hour – the initial speed of the body;
u2 = 27 kilometers per hour – the speed of the body through the time interval t.
It is required to determine a (m / s2) – body acceleration.
Let’s convert the units of speed to the SI system:
u1 = 36 km / h = 36 * 10/36 = 10 meters per second.
u2 = 27 km / h = 27 * 10/36 = 7.5 meters per second.
Then, to determine the acceleration of the body, you must use the following formula:
a = (u2 – u1) / t;
a = (7.5 – 10) / 5 = -2.5 / 5 = -0.5 m / s2 (negative sign of acceleration means that the movement of the body is equally slow).
Answer: the acceleration of the body is equal to -0.5 m / s2.