Newton's Second Law with Numbers
Treating F = ma as a working equation: the resultant force sets the acceleration, and mass measures how strongly an object resists that change. Mass, not weight, is what appears in the calculation.
What a learner can do afterwards
- Calculates any one of resultant force, mass or acceleration when the other two are given
- Explains why a loaded trolley accelerates less than an empty one under the same push
- Uses the resultant of several forces, not one single force, in the calculation
1 · Read
Newton's second law fits in one line: resultant force equals mass times acceleration. Push twice as hard and you get twice the acceleration. Keep the push the same but double the mass, and the acceleration halves.
Resultant means the single force left after every push and pull is combined, so always combine first and calculate second. Draw the object with every force as an arrow, pick a direction to call positive, then feed the total into F equals m a, with mass in kilograms.
A loaded trolley accelerates less than an empty one under the same push, since more mass resists the change. Friction and drag join the arrows too, so the resultant can be far smaller than the push you apply. Say the forces in words first; if the words make sense, the sum usually follows.
Watch the units and the signs. Mass goes in as kilograms and acceleration comes out in metres per second squared. A quick sketch stops sign mistakes before they happen, especially when friction points against the motion.
Combine forces into one resultant, then let F equals m a do the rest.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.