Newton's Laws and Forces
Aligned to HS-PS2 — Next Generation Science Standards.
What this lesson teaches
Newton's laws describe motion: objects resist changes (inertia), force equals mass times acceleration (F=ma), and forces come in equal-and-opposite pairs.
Worked examples
Example 1
Pushing a 2 kg cart with 10 N of force gives acceleration a = F/m = 10/2 = 5 m/s².
Example 2
The same 10 N on a 20 kg cart gives a = 10/20 = 0.5 m/s² — ten times the mass, a tenth the acceleration.
Example 3
A net force of zero does not mean at rest. A car at a steady 60 mph has balanced forces, exactly like a parked one.
Practice questions
- State Newton's second law as an equation.
- If you double the force on an object, what happens to acceleration?
- Give an example of action-reaction forces.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Las Leyes de Newton y las Fuerzas
Las leyes de Newton describen el movimiento: los objetos se resisten a los cambios (inercia), la fuerza es igual a la masa multiplicada por la aceleración (F=ma), y las fuerzas actúan en pares iguales y opuestos.
Ejemplo 1: Empujar un carrito de 2 kg con una fuerza de 10 N produce una aceleración a = F/m = 10/2 = 5 m/s².
Ejemplo 2: Los mismos 10 N en un carro de 20 kg dan a = 10/20 = 0.5 m/s² — diez veces la masa, la décima parte de la aceleración.
Ejemplo 3: Una fuerza neta de cero no significa en reposo. Un coche a 60 mph constantes tiene fuerzas equilibradas, igual que uno estacionado.
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