GED Science TestPhysical ScienceMedium
A car with a mass of 1200 kg is traveling at a speed of 25 m/s. The driver applies the brakes, and the car comes to a complete stop in 4 seconds. What is the average braking force applied to the car?
- A12500 N
- B3000 N
- C12000 N
- D7500 N
Show answer & explanationAnswer & explanation
Correct answer: D. 7500 N
First, calculate acceleration (a = Δv/Δt): a = (0 m/s - 25 m/s) / 4 s = -6.25 m/s². Then, use Newton's Second Law (F = ma): F = 1200 kg * -6.25 m/s² = -7500 N. The magnitude of the braking force is 7500 N.
Why the other options are wrong
- A. Incorrect calculation, likely misusing the given values or formula.
- B. Incorrect calculation, perhaps only dividing mass by time.
- C. This would be the force if acceleration was 10 m/s² (1200 * 10 = 12000), which is incorrect.
Newton's Second Law of Motion
The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass (F=ma).
- F = ma (Force = mass × acceleration)
- Force measured in Newtons (N)
- Mass in kilograms (kg), acceleration in m/s²
Memory trick: Force equals Mass times Acceleration, 'F ma' like 'Fuh-mah!'