What is Newton's Second Law of Motion?

Newton's Second Law states that the net force acting on an object is equal to its mass multiplied by its acceleration: F = ma. Force is measured in newtons (N), mass in kilograms (kg) and acceleration in metres per second squared (m/s²). This means a larger force produces greater acceleration for a given mass, and a more massive object requires more force to achieve the same acceleration.

What is the difference between mass and weight?

Mass is the amount of matter in an object, measured in kilograms (kg). It is constant regardless of location. Weight is the gravitational force acting on an object, measured in newtons (N), calculated as W = mg where g is gravitational field strength. On Earth, g = 9.81 m/s², so a 70 kg person weighs 70 × 9.81 = 686.7 N. On the Moon (g = 1.62 m/s²), their weight would be only 113.4 N, but their mass remains 70 kg.

How do you calculate gravitational force?

Gravitational force (weight) is calculated using W = mg, where m is mass in kg and g is gravitational field strength in N/kg (or m/s²). On Earth, g = 9.81 N/kg. On the Moon g = 1.62 N/kg, Mars g = 3.72 N/kg, Jupiter g = 24.8 N/kg. For gravitational force between two masses, use Newton's Law of Gravitation: F = Gm₁m₂/r², where G = 6.674 × 10⁻¹¹ N m² kg⁻².

What is terminal velocity?

Terminal velocity is the constant speed reached by a falling object when the drag force (air resistance) equals the gravitational force (weight), so net force is zero and acceleration becomes zero. From F = ma, if F = 0 then a = 0, meaning the object falls at constant velocity. Terminal velocity depends on mass, cross-sectional area and drag coefficient. A skydiver in freefall reaches approximately 55 m/s (120 mph) in a spread-eagle position.

How do you calculate net force with multiple forces?

Net force is the vector sum of all forces acting on an object. For forces in the same direction, add them. For opposite directions, subtract. For forces at angles, use vector components (resolve into horizontal and vertical components using trigonometry, sum each component, then use Pythagoras to find magnitude). From Newton's Second Law, the net force = mass × acceleration, so an object accelerates in the direction of the net force.

What is the unit of force?

The SI unit of force is the newton (N), named after Sir Isaac Newton. One newton is defined as the force required to accelerate a mass of one kilogram at one metre per second squared: 1 N = 1 kg m/s². Other units include kilonewtons (kN = 1,000 N) used in engineering, and pound-force (lbf) used in some imperial contexts where 1 lbf ≈ 4.448 N.

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