To calculate the force required to stop a car, we can use the equation:
Force = (mass * change in velocity) / time
Given:
Mass of the car = 800 kg
Initial velocity = 20 m/s
Final velocity (since the car is stopping, the final velocity is 0 m/s)
Distance traveled = 25 m
Time taken = 2.5 seconds
First, we need to find the change in velocity:
Change in velocity = final velocity - initial velocity
Change in velocity = 0 m/s - 20 m/s
Change in velocity = -20 m/s
Next, we can calculate the force using the equation:
Force = (mass * change in velocity) / time
Force = (800 kg * -20 m/s) / 2.5 seconds
Force = -16000 kg·m/s / 2.5 seconds
Force = -6400 N
Therefore, the force required to stop the car is 6400 N. Option b) 6400 N is the correct answer.