Edexcel Physics IGCSE: Forces and Motion

Questions and Answers

Explain how the presence of air resistance affects the motion of a body in free fall.

Air resistance opposes the weight of the falling body, reducing the resultant force and acceleration until terminal velocity is reached.

Define the term 'stopping distance' in relation to driving.

Stopping distance is the total distance a vehicle travels from the moment the driver perceives a hazard until it comes to a complete stop.

What factors can increase a driver's thinking distance?

Greater speed, slower reaction time due to alcohol, tiredness, or distractions.

Differentiate between elastic and plastic deformation.

Elastic deformation allows the object to return to its original shape after the load is removed, while plastic deformation causes a permanent change in shape. Signup and view all the answers

How does increased speed affect the braking distance of a vehicle?

Increased speed leads to a longer braking distance due to higher kinetic energy that must be overcome. Signup and view all the answers

What is terminal velocity and how is it reached during free fall?

Terminal velocity is the constant speed achieved when the force of gravity is balanced by air resistance, resulting in no net acceleration. Signup and view all the answers

State Newton's first law of motion and relate it to a body in free fall.

Newton's first law states that an object remains at rest or in uniform motion unless acted upon by a net external force, which applies to a falling body as gravity acts on it. Signup and view all the answers

Identify two factors that can reduce a vehicle's braking efficiency.

Poor road conditions (like icy or wet surfaces) and worn mechanical parts (such as tires or brake pads). Signup and view all the answers

Explain the relationship between acceleration and resultant force in a falling object.

As the resultant force decreases due to air resistance, the acceleration of the falling object also decreases. Signup and view all the answers

What is the significance of the resultant force when a vehicle is in motion?

The resultant force determines the vehicle's acceleration; if it is zero, the vehicle moves at constant speed. Signup and view all the answers

Study Notes

Movement and Position

Speed is defined as the distance travelled per unit time.
Acceleration occurs when speed changes; free fall acceleration near Earth is constant.
Velocity includes direction in addition to speed.
Acceleration formula: ( a = \frac{v - u}{t} ) where ( v ) is final velocity, ( u ) is initial velocity, and ( t ) is time.
Distance-time graphs show that:
- Gradient represents velocity.
- A negative gradient indicates returning to the start.
- A horizontal line indicates stationary motion.
- A curved line suggests changing velocity.
Velocity-time graphs show that:
- Gradient represents acceleration.
- A negative gradient indicates deceleration.
- A horizontal line signifies constant speed.
- The area under the line represents the distance travelled.

Forces, Movement, Shape, and Momentum

Vectors have both magnitude and direction, while scalars have only magnitude.
Examples include:
- Scalars: distance, speed, time, energy.
- Vectors: displacement, velocity, acceleration, force.
Forces can change an object's speed, shape, or direction, measured in Newtons (N).
Friction impedes motion between surfaces and causes heating; air resistance is a type of friction.
Resultant forces are found by adding forces in the same direction and subtracting opposites.
Newton's Laws of Motion:
- First Law: An object at rest or constant velocity remains so unless acted upon by a resultant force.
- Second Law: ( F = ma ) where ( F ) is force, ( m ) is mass in kilograms, and ( a ) is acceleration.
- Third Law: Every action force has an equal and opposite reaction force.
Weight is the gravitational force on an object: ( W = mg ), where ( g ) is the gravitational field strength (10 N/kg on Earth).

Motion in a Gravitational Field

In free fall:
- Initially, only weight acts (no air resistance).
- As speed increases, air resistance builds up, reducing downward acceleration.
- When the forces balance, terminal velocity is reached, and there is no further acceleration.

Stopping Distance

Thinking distance is the distance travelled before reacting; increases with:
- Higher speed.
- Slower reaction times due to alcohol, fatigue, or distractions.
Braking distance is the distance from when brakes are applied until stopping; increases with:
- Higher speed or mass.
- Poor road or vehicle condition (e.g., worn tires).
Stopping distance is the sum of thinking distance and braking distance.

Deformation of Bodies

Objects can undergo deformation (changes in size or shape) when forces are applied.
Elastic deformation allows an object to return to its original shape when the force is removed, such as stretching a spring.

Description

This quiz covers Topic 1 of the Edexcel Physics IGCSE syllabus focusing on Forces and Motion. It provides essential summary notes that highlight key concepts and principles in physics. Prepare yourself for a better understanding of motion, forces, and their applications.