Force and Acceleration

This section delves into the relationship between force, mass, and acceleration, introducing Newton's Second Law and the concept of inertia.

Definition: Newton's Second Law of Motion states that the acceleration of an object is proportional to the resultant force acting on it and inversely proportional to its mass.

The formula for Newton's Second Law is presented:

Resultant force, F (Newtons) = mass, m (kg) x acceleration, a (m/s^2)

Vocabulary: Inertia is defined as the tendency of an object to resist changes in its state of motion.

The section also explains how velocity changes in relation to the direction of the resultant force:

• When the resultant force is in the same direction as velocity, the object speeds up.
• When the resultant force is in the opposite direction to velocity, the object slows down.

Weight and Terminal Velocity

This part of the document explores the concepts of weight, mass, and terminal velocity.

Definition: Weight is the force acting on an object due to gravity, measured in Newtons (N).

The relationship between mass and weight is explained, introducing the concept of gravitational field strength:

Weight, W (N) = mass, m (kg) x gravitational field strength, g (N/kg)

Highlight: Earth's gravitational field strength at the surface is approximately 9.8 N/kg.

The concept of terminal velocity is introduced, explaining how it occurs when the frictional force on a falling object equals its weight, resulting in zero acceleration.

Forces and Braking

This section discusses the forces acting on vehicles and the factors affecting braking distances.

Example: For a car traveling at constant velocity, the driving force of the engine is balanced by resistive forces, primarily air resistance.

The document explains that the braking force required to stop a vehicle depends on:

1. The speed of the vehicle when brakes are first applied
2. The mass of the vehicle

The concept of stopping distance is introduced, which consists of:

1. Thinking distance
2. Braking distance

Highlight: Stopping distance = Thinking distance + Braking distance

Factors affecting stopping distance are discussed, including:

• Driver's condition (tiredness, alcohol, drugs)
• Vehicle speed
• Road conditions
• Vehicle maintenance

The section also introduces the equation for calculating deceleration:

v^2 = u^2 + 2as

Where: s = distance u = initial speed v = final speed a = acceleration (or deceleration)

Momentum

This part introduces the concept of momentum and its conservation in collisions.

Definition: Momentum of a moving object, p (kg m/s) = mass, m (kg) x velocity, v (m/s)

Highlight: Momentum is a vector quantity, having both magnitude and direction.

The law of conservation of momentum is explained:

Quote: "In a closed system, the total momentum before an event is equal to the total momentum after the event."

The document emphasizes that momentum is conserved in any collision as long as no external forces act on the objects involved.

This comprehensive overview of force and motion provides students with essential knowledge for AQA GCSE Physics exams, covering key topics such as Newton's laws, terminal velocity, and momentum conservation.