Newton’s first law states that objects do not change their state of motion until met with an unbalanced force. Newton’s second law discusses the way in which another type of force, net force, impacts an object’s acceleration.
Remember, net force is the sum of all the forces acting on an object. So how does net force affect the acceleration of an object? The answer brings up another Newtonian term you’ve learned: mass. The way force and mass impact acceleration can be described by one of the following two equations: We can say that an object’s net force (which is referred to as "F") is equal to the product of mass and acceleration (F=MA); or, as the animation you’re about to view describes it, acceleration is equal to the net force on an object divided by the mass of that object, or A=F/M.
Before you watch the animation, review the vocabulary you learned on Page 2. In particular, the terms mass, acceleration, and net force will be coming into play.
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Manager: Newton’s first law asks: What happens when there is no force acting on an object? And the answer is, inertia.
Newton’s second law asks: What happens when thereis a net force acting on an object? And the answer is, acceleration. To be more exact, the law says that acceleration is equal to the net force someone puts on an object, divided by the mass of that object. So here’s an object. And here’s someone who can apply some force.
Even though this is a baseball, we’re going to put an “M," for mass, on it, because mass is a huge part of the second law. We’re going to call the net force the pitcher puts on the ball "F." And when the ball leaves the pitcher’s hand it moves with ”A” for acceleration.
I’m giving the pitcher the ball, which again is the mass.
He’s working up some force to put on that mass.
Nice pitch, dude. Alright, let’s get the bowling ball out here.
Pitcher: Huh?
Manager: So let’s say you put the same amount of force on the bowling ball. What’s going to happen?
Pitcher: Um, my arm is gonna fall off?
Manager: Hah, no. You’re going to put the same force on the bowling ball as you did on the baseball. So that’s going to affect the acceleration, right?
Pitcher: Mm, okay, whatever.
Manager: Let that ball rip, same as before. The bowling ball didn’t go as far. Its acceleration dropped, even though the same force was applied to it. Same force, but 50 times the mass; the acceleration drops, a lot. Let’s write it out.
That awesome acceleration you achieved with the baseball; you got that acceleration by throwing the baseball with your net force. If that’s a math equation, you’re actually dividing the net force you put on the ball by the mass of the ball itself.
Then, that not-so-awesome acceleration you achieved with the bowling ball?
You got that by applying the same net force you had put on the baseball onto the bowling ball, which has a mass that is 50 times greater than the mass of the baseball. So if you take the 50 out of this side, you find… yup, the acceleration from the bowling ball pitch is 1/50th the acceleration of the baseball pitch. Much slower.
That’s Newton’s second law in action. Acceleration equals net force divided by mass.
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Write one or two sentence in which you apply Newton’s second law to another sport, such as soccer, football, or hockey. Alternatively, apply the law to another real-life situation, such as pushing light and heavy objects across a wood floor, or an activity you choose yourself.