Question

A car traveled at a constant velocity of 70 mph from noon to 2:00 pm. At 3:00 pm the velocity of the car was 80 mph; and finally at 4:30 pm the velocity of the car was 40 mph.

Which statement accurately describes the acceleration of the car?

A) The car had a positive acceleration the entire time.
B) The car had a negative acceleration from noon to 2:00 pm.
C) The acceleration of the car from 3:00 pm to 4:30 pm was zero
D) The car had a positive acceleration between 2:00 pm and 3:00 pm.

Answer 1

That answer is D. The car had a positive acceleration between 2:00 pm and 3:00pm

Answer 2

Answer: The correct option is D.

Explanation: Acceleration is defined as the ratio of velocity over time.

Positive acceleration is defined as the increase in the velocity over a time period.

Negative acceleration is defined as the decrease in the velocity over a time period.

In the given question,

• The velocity of the car increases in the time interval 2:00 pm to 3:00 pm from 70 mph to 80 mph. Hence, the car will have a positive acceleration during this time interval.

• In the time interval from 3:00 pm to 4:30 pm, the velocity is decreasing from 80 mph to 40 mph. So, the car will experience a negative acceleration.

Hence, the correct option is D.