Question

A driver slams on his brakes to avoid hitting a dog that ran out into the street. The car, traveling at 48 m/s, comes to a complete stop in 4 seconds. What is the acceleration of the car?

A) 6 m/s².
B) 12 m/s².
C) 24 m/s².
D) 48 m/s².

Answer 1

To find the car's acceleration, use the formula a = Δv/Δt. With an initial velocity of 48 m/s and stopping in 4 seconds, the acceleration is calculated to be -12 m/s². The magnitude of this deceleration is 12 m/s².

Step-by-step explanation:

To calculate the acceleration of the car, we can use the formula derived from the equations of motion: a = Δv/Δt, where Δv is the change in velocity and Δt is the change in time.

The car comes to a complete stop, so the final velocity (vf) is 0 m/s, and the initial velocity (vi) is given as 48 m/s. The time it takes for this change (Δt) is 4 seconds.

Using the formula a = Δv/Δt = (vf - vi) / Δt, we plug in the values:
a = (0 m/s - 48 m/s) / 4 s = -48 m/s / 4 s = -12 m/s².

The negative sign indicates that the car is decelerating, which is expected since it is coming to a stop. However, since the question asks for the magnitude of the acceleration, we can report the answer as 12 m/s², which corresponds to option B).