Video: Using Newton’s Second Law to Find the Average Force for a Constant Acceleration

Your 1500-kg sports car accelerates from 0 to 30 m/s in 10 s. What average force is exerted on it during this acceleration?

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Video Transcript

Your 1500-kilogram sports car accelerates from zero to 30 meters per second in 10 seconds. What average force is exerted on it during this acceleration?

Let’s call that average force 𝑓 sub avg. And as we approach this problem, let’s recall Newton’s second law of motion. This second law says that the net force acting on an object is equal to the mass of that object multiplied by its acceleration. Let’s further recall the definition for acceleration. An object’s acceleration is defined as its change in velocity divided by the change in time. In our particular case, we’re told that the change in the car’s velocity is 30 meters per second and that this change occurs in 10 seconds. So the acceleration of the sports car is 3.0 meters per second squared.

Now let’s look back at Newton’s second law and apply it to our situation. The average force exerted on the sports car is equal to its mass times its acceleration. We’ve just solved for the acceleration 𝑎, and we’re given the mass of the car in the problem statement.

When we insert those two values and multiply them together, we find an average force, to two significant figures, of 4.5 times 10 to the third newtons. That’s the average force exerted on the car.

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