Answer:
A. 6000 N
Explanation:
Set Up: Let the origin be at the location of the car when the force is applied & the +x direction be in the direction the car is traveling.
List the known & unknown quantities:
mass of the car m = 900 kg
υx = 0 since the force stops the car
υ0x = 20 m/s
x – x0 = 30 m
Fx = force = ?
Solve: First find the acceleration of the car, ax:
υx2 = υ0x2 + 2ax(x – x0)
ax= υx2⎯ υ0x2/2(x⎯x0) = (0 m/s)2⎯(20 m/s)2/2(30 m) =⎯6.67 m/s2
Now find the force using Newton’s second law.
∑Fx=max=(900 kg) (⎯6.67 m/s2)=⎯6000 N
