Question

A 1000 kg car travels on a highway with a speed of 30 m/s. The driver sees a roadblock and applies the brakes, which provide a
constant braking force of 4 kN. What is the acceleration of the car?
A. 4 m/s​

Answer 1

Answer:

-4m/s

Explanation:

use the formula

$f = ma$

where f-force

m-mass

a-accleration

so

1kN=1000N

so apply

4000=1000×a

a=4m/s

(the negative is because the car was braking)

Answer 2

Answer:

Your answer is -4 m/s^2

Explanation:

Set Up: Let +x be the direction the car is traveling.  

List the known & unknown quantities:  

   m = mass of the car = 1000 kg

  υ = 30 m/s

  Fx = –4 kN = –4000 N (negative since it is a braking force)

  ax = acceleration =?  

Solve: Use Newton’s second law of motion.  

Fx=max    

ax=Fx/m = −4000 N /1000 kg = −4000 kg·m/s^2 / 1000 kg =−4m/s^2