The negative acceleration of the truck is -2 m/s.
Acceleration of the body is the rate of change of speed with respect to time. The acceleration of the body is calculated by dividing the change in speed during a particular interval of time, by the time taken to change the speed.
According to the question, the initial speed of the truck is 40 m/s and it decreases to 20 m/s after 10 seconds. As the speed of the truck is decreasing, its sign is negative.
So given in the question
Initial Speed= u = 40 m/s
Final Speed= v = 20 m/s
Change in velocity = v - u
= 20 - 40
= -20 m/s
Time interval = 10 seconds
Acceleration = Change in Velocity/Time interval
= -20/10
= -2 m/s
So the acceleration of the truck is equal to -2 m/s. The negative sign indicates the speed is decreasing.
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