Final answer:
The average force required to stop an 820 kg car in 4.0 s traveling at 95 km/h is -5410.05 N, rounded to B. -5,300 N according to the options provided.
Step-by-step explanation:
The student asked about the average force required to stop an 820 kg car in 4.0 seconds if the car is travelling at 95 km/h. To solve this problem, we need to use the formula for force, which is the change in momentum (Δp) over time (Δt), where momentum is mass (m) times velocity (v).
First, convert the speed from km/h to m/s by multiplying by (1000 m/1 km)/(3600 s/1 h), which gives us 26.39 m/s. The change in momentum is m×v, which for this car is 820 kg × 26.39 m/s = 21640.2 kg·m/s. Now, to find the average force, divide the change in momentum by the time, which is 21640.2 kg·m/s / 4.0 s = -5410.05 N.
The negative sign indicates that the force is in the opposite direction of the car's initial motion. Therefore, the average force required to stop the car is -5410.05 N, which when rounded to the nearest ten, as per the options given, is B. -5,300 N.