Newton's Second Law, also known as the Law of Acceleration, states that the acceleration of an object depends on the net force applied to it and its mass. In simple terms, if you apply more force to an object, it will accelerate more, and if the object has more mass, it will accelerate less for the same amount of force.
To better understand this law, let's look at ten practical examples:
1. Pushing a supermarket cart
When you push an empty grocery cart, it is easy to move because it has little mass.
If you apply a force to an empty car, it will accelerate rapidly. If the cart is full of purchases and weighs more, with the same force applied, the acceleration will be much less.
This shows how mass affects acceleration: the greater the mass, the less acceleration for the same force.
2. Throw a baseball
Suppose you throw a baseball very hard. The ball has little mass, so it will accelerate much faster than a heavier object.
This example demonstrates how a considerable force can produce a high acceleration in an object of small mass.
3. Stop a car
When a car brakes, a force is applied backwards to reduce its speed. If a heavy car is braked with significant force, its deceleration will be proportional to the force applied and the mass of the car.
In this case, the kinetic energy of the vehicle is converted into thermal energy that is dissipated into the environment due to the friction force of the brakes.
4. Drag a box on the floor
Imagine you are dragging a box along the ground by applying a force. If the box has little mass, it will move faster. If the box is heavier and you apply the same force, the acceleration will be less.
In this example, the resulting force that is applied in the formula of Newton's second law is the force applied by us minus the friction force of the ground, which is always opposite to the direction of movement.
5. Running with a backpack
If you run with a light backpack on your back and apply a forward force, the acceleration will be high. If you are carrying a heavier backpack, the same force applied will result in a lower acceleration.
If you are also climbing a mountain, you must overcome the force of gravity proportionally to the mass of the backpack.
6. Climb a mountain by bike
When cycling up a mountain, you need to apply enough force to overcome the gravity and resistance of the terrain, just like with the backpack in the previous example.
If you and your bike have little mass, the upward acceleration will be greater. If you are carrying more load and the total mass is greater, the same force will result in a smaller acceleration.
On the other hand, you will also have to exert a horizontal force greater than the friction force with the ground and the bearings to obtain linear acceleration.
7. Take off on a plane
During takeoff, an aircraft needs to generate enough force to overcome gravity and reach flight speed. If the aircraft has a large mass, it needs considerable force to accelerate.
The relationship between the applied force and the mass of the plane determines its acceleration during takeoff. For this reason, the aircraft load must be considered so that it is not excessive in relation to the engine power.
8. Launch a rocket into space
A rocket launch is an excellent example of Newton's Second Law. A rocket, when launched, requires a large amount of force to overcome gravity and air resistance. If the rocket has significant mass, it will need a large force to achieve high acceleration.
As the rocket burns fuel and loses mass which means the acceleration increases if the force remains constant. Furthermore, as it moves away from the center of the Earth, the gravitational force decreases with distance, contributing to increasing the acceleration of the rocket.
9. Push a chair
If you push a light chair, it will move easily with little force. If the chair is heavier or someone is sitting on it, the same amount of force will produce less acceleration.
This example is easily reproducible to show how the mass of the object affects the acceleration when a force is applied.
10. Free fall with air resistance
In the free fall of an object, the net force includes gravity and air resistance.
If a ball falls with a force of gravity and the air resistance is significant, the acceleration of the fall will be less than if there were no air resistance according to the laws that regulate fluid mechanics.