Physics Gateway (OCR)
1.Forces and Motion
This topic focuses on understanding how forces affect objects' motion. It covers the following:
Speed and Velocity:
Speed is a scalar quantity that measures how fast an object is moving.
Formula:
Velocity is a vector quantity that specifies both the speed and direction of an object.
Formula:
Acceleration:
Acceleration refers to the rate of change of velocity over time.
Formula:
Newton’s Laws of Motion:
First Law (Law of Inertia): An object remains at rest or in uniform motion unless acted upon by an external force.
Second Law: The force acting on an object is equal to its mass times its acceleration.
Formula:
Third Law: For every action, there is an equal and opposite reaction.
Weight and Mass:
Weight is the force exerted by gravity on an object, given by:
Formula:
Where m is mass and g is the gravitational field strength (approx. 9.8 N/kg on Earth.
Resultant Force:
The resultant force is the single force that can replace a system of forces acting on an object without changing its effect. If multiple forces are acting on an object, the resultant force determines the object’s acceleration.
For example, if a car is being pushed by two people, one at the front and one at the back, the total force acting on the car is the sum of both forces if they are acting in the same direction.
Momentum:
Momentum is the product of an object’s mass and velocity:
Understanding momentum helps explain collisions and impacts. Conservation of momentum states that in an isolated system (no external forces), the total momentum before and after an event (like a car crash) remains constant.
Inelastic and Elastic Collisions:
In an elastic collision, both kinetic energy and momentum are conserved.
In inelastic collisions, only momentum is conserved, and kinetic energy is lost (often transformed into heat or sound).
2. Energy and Power
This section involves understanding different forms of energy and their transformations, along with the concept of power.
Kinetic Energy (KE):
The energy possessed by an object due to its motion.
Formula:
Where m is mass and v is velocity.
Potential Energy (PE):
The energy stored due to an object’s position, such as gravitational potential energy.
Formula:
Where m is mass, g is gravitational field strength, and h is height.
Work Done:
Work is done when a force moves an object in the direction of the force.
Formula:
Where F is force and d is distance.
Power:
Power is the rate at which work is done or energy is transferred.
Formula:
Where W is work and t is time.
Law of Conservation of Energy:
Energy cannot be created or destroyed; it can only be transformed from one form to another.
Gravitational Potential Energy:
The energy stored in an object due to its position in a gravitational field. The higher an object is above the ground, the more the gravitational potential energy it has.
Formula:
Where m is mass (kg), g is gravitational field strength (9.8N/kg on Earth) and h height above the ground (m).
Kinetic Energy and Work-Energy Principle:
When work is done on an object (i.e., a force causes displacement), energy is transferred, which can be seen in the object’s change in kinetic energy. For example, when a car accelerates, its kinetic energy increases, and work is done by the engine.
Power and Efficiency in Machines:
In real-world machines, efficiency is a key factor in understanding how much input energy is transformed into useful output energy. For example, a light bulb may use 100 J of electrical energy, but only 20 J is converted into light; the rest is wasted as heat.
3. Waves and Sound
This section involves the study of wave behavior and properties, including sound waves.
Wave Properties:
Amplitude: The maximum displacement from equilibrium (height of the wave).
Wavelength (λ): The distance between two successive points in phase (e.g., crest to crest).
Frequency (f): The number of complete oscillations or cycles per second.
Formula:
Where T is the period.
Wave Speed (v):
Formula:
Where V is the wave speed, f is frequency, and λ is wavelength.
Sound Waves:
Sound is a longitudinal wave that requires a medium (such as air or water) to travel through.
The speed of sound depends on the medium and temperature.
The Electromagnetic Spectrum:
Electromagnetic waves range from radio waves (longest wavelength) to gamma rays (shortest wavelength). The spectrum includes visible light, microwaves, infrared radiation, and more.
Reflection, Reflection, and Diffraction:
Reflection: When a wave bounces off a surface.
Refraction: When a wave changes direction as it passes from one medium to another (e.g., light bending as it moves from air to water).
Diffraction: The spreading out of waves as they pass through an opening or around an obstacle.
4. Electricity and Magnetism
This topic covers the fundamental principles of electricity and magnetism.
Electric Current:
Current (I): The flow of electric charge.
Formula:
Where Q is the charge and t is time.
Ohm’s Law:
The relationship between voltage, current, and resistance in an electrical circuit.
Formula:
Where V is voltage, I is current, and R is resistance.
Power in an Electrical Circuit:
The rate at which electrical energy is used.
Formula:
Where P is power, I is current, and V is voltage.
Magnetic Fields:
A magnetic field is created by moving electric charges (current) and exerts a force on other magnetic materials or moving charges.
Electromagnetism:
The interaction between electric currents and magnetic fields, demonstrated by devices like electromagnets.
5. Energy Resources and Transfer
Energy Efficiency:
Efficiency measures how well energy is converted into useful work.
Formula:
Useful Energy Output/Total Energy Input x 100%
No energy conversion is 100% efficient due to energy losses (usually as heat).
Renewable and Non-Renewable Energy:
Renewable: Can be replenished naturally (solar, wind, hydro, geothermal).
Non-Renewable: Limited supply (coal, oil, natural gas).
Power Stations:
Fossil Fuel Power Stations: Burn coal or gas to produce steam that drives turbines.
Nuclear Power Stations: Use nuclear fission to produce heat, which generates steam.
Hydroelectric Power Stations: Use water flowing from a height to turn turbines and generate electricity.