### Laws Of Motion Newtons Second And Third Laws Of Motion

# Newton’s Second Law of Motion

**Key Concepts:**

- The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
- Equation:
**F = ma**(F = net force, m = mass, a = acceleration) - SI unit of force: newton (N) = force required to accelerate 1-kg mass at 1 m/s²
- Used to solve motion problems (acceleration, force, distance traveled)
- Defines momentum (product of mass and velocity)
- Impulse of a force = force × time = change in momentum
- Momentum is conserved (total momentum of a closed system remains constant)

# Newton’s Third Law of Motion

**Key Concepts:**

- For every action, there is an equal and opposite reaction.
- Equation:
**F_action = -F_reaction**(F_action = force from first object on second, F_reaction = force from second object on first) - Used to solve problems involving interactions between objects (forces exerted, motion)
- Explains phenomena like walking (ground pushing back on foot propels person forward)
- Balanced forces: net force on an object is zero, no acceleration