Question

A car's brakes produce -7 m/s² acceleration. How long will it take to change its speed from 84 m/s to 42 m/s south?

A) 6 seconds
B) 7 seconds
C) 8 seconds
D) 9 seconds

Answer 1

The car will take 6 seconds to change its speed from 84 m/s to 42 m/s south.

Step-by-step explanation:

To find the time it takes for the car to change its speed from 84 m/s to 42 m/s south, we can use the formula:

time = change in velocity / acceleration

In this case, the change in velocity is 42 m/s - 84 m/s = -42 m/s (since it is in the opposite direction).

Given that the acceleration is -7 m/s², the time can be calculated as:

time = -42 m/s / -7 m/s² = 6 seconds

Therefore, the correct answer is A) 6 seconds.