Question

while travelling south on an expressway, a car travelling 60 mph (miles per hour) slows down to 30 mph in 12 minutes due to traffic conditions. calculate the acceleration.
a =
-6.0
-2.5
-450
-150
mi/h²

Explanation:

Step1: Recall the acceleration formula

Acceleration \( a \) is given by the change in velocity \( \Delta v \) divided by the change in time \( \Delta t \), i.e., \( a=\frac{\Delta v}{\Delta t} \).

Step2: Determine initial and final velocities

Initial velocity \( v_i = 60 \) mph, final velocity \( v_f = 30 \) mph. So, \( \Delta v=v_f - v_i=30 - 60=- 30 \) mph.

Step3: Convert time to hours

The time is 12 minutes. Since 1 hour = 60 minutes, \( \Delta t=\frac{12}{60}=0.2 \) hours.

Step4: Calculate acceleration

Substitute \( \Delta v=-30 \) mph and \( \Delta t = 0.2 \) h into the acceleration formula: \( a=\frac{-30}{0.2}=-150 \) \( \text{mi/h}^2 \).

Answer:

-150