Final answer:
The magnitude of the average force that acted on a 1250-kg car to bring it to rest from 18 m/s in 0.30 s is 75000 N. This is calculated using the formula for force based on Newton's second law of motion.
Step-by-step explanation:
To calculate the magnitude of the average force that brought a 1250-kilogram car traveling at 18 meters per second to rest in 0.30 seconds, we can use the formula derived from Newton's second law of motion:
F = ma, where F is the force, m is the mass, and a is the acceleration.
First, we need to find the acceleration, which can be determined by the change in velocity over time.
Acceleration (a) is given by the formula: a = (v_f - v_i) / t, where:
v_f = final velocity (0 m/s since the car comes to rest),
v_i = initial velocity (18 m/s),
t = time (0.30 s).
Plugging in the values, we get:
a = (0 m/s - 18 m/s) / 0.30 s = -60 m/s2.
The negative sign indicates the car is decelerating. Now, we can calculate the force:
F = m * a = 1250 kg * (-60 m/s2) = -75000 N.
The negative sign indicates the direction of the force is opposite to the motion of the car. The magnitude of the force is 75000 N.
Therefore, the correct answer is B) 75000 N.