Newton’s Second Law
Newton’s Second Law explains the relationship between the force applied to an object, its mass, and the acceleration that results. It forms the cornerstone of classical mechanics by quantifying how objects speed up, slow down, or change direction when forces act upon them.
The Law in Mathematical Terms
Where:
- F = Net force (Newtons, N)
- m = Mass (kilograms, kg)
- a = Acceleration (meters per second squared, m/s²)
Interpreting the Equation
This equation tells us that:
- Applying a larger force causes greater acceleration.
- An object with more mass accelerates less for the same force.
- The acceleration points in the direction of the net force.
Units and Definitions
The Newton (N) is defined as the force needed to accelerate 1 kg of mass by 1 m/s²:
Example Problem
Question: A 5 kg object is pushed with a net force of 20 N. What is its acceleration?
Solution:
Use the rearranged formula to solve for acceleration:
The object accelerates at 4 meters per second squared.
Applications in Real Life
Newton’s Second Law explains many everyday phenomena:
- Why heavier cars need stronger engines to accelerate.
- How athletes push off the ground to jump higher.
- Why astronauts feel weightless when forces balance out in orbit.
Common Confusions
- Force is not the same as acceleration. Force causes acceleration but they’re distinct physical quantities.
- Mass and weight differ. Mass is the amount of matter, weight is gravitational force on that matter.
- Acceleration direction matters. It aligns with the net force direction, even if the object slows down.
Try It Yourself: Calculate Force
Input the mass and acceleration below to calculate the net force: