A car traveling due east at 20 m/s reverses its direction over a period of 10 seconds so that it is now traveling due west at 20 m/s. What is the direction of the car’s average acceleration over this period?
a- The car’s average acceleration points due west.
b- The car’s average acceleration is zero.
c- The car’s average acceleration points due east.
d- The direction of the car’s average acceleration cannot be determined from the given information.
A: west
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The direction of the car's average acceleration can be determined by considering its change in velocity over time.
When the car is traveling due east at 20 m/s, its velocity is positive. When it reverses direction and begins traveling due west at 20 m/s, its velocity becomes negative.
Acceleration is the rate at which velocity changes over time. In this case, the car's velocity changes from positive to negative, indicating a change in velocity in the negative direction.
Therefore, the car’s average acceleration points due west.
The correct answer is a- The car’s average acceleration points due west.
To find the direction of the car's average acceleration, we need to determine the change in velocity and the time over which this change occurs.
Given that the car travels due east at 20 m/s and then reverses its direction and travels due west at 20 m/s, we can determine the change in velocity:
Change in velocity = Final velocity - Initial velocity
Change in velocity = (-20 m/s) - (20 m/s) = -40 m/s
The change in velocity is -40 m/s, indicating that the car's velocity is decreasing.
The time over which this change occurs is given as 10 seconds.
The average acceleration of an object is defined as the change in velocity divided by the time taken:
Average acceleration = Change in velocity / Time
Average acceleration = -40 m/s / 10 s = -4 m/s^2
The negative sign in the average acceleration indicates that the car's velocity is decreasing, which means it is decelerating or accelerating in the opposite direction.
Therefore, option a- The car's average acceleration points due west is the correct answer.