A Level Physics WJEC

Motion, Energy and Matter: Basic Physics

Basics of Motion

• Displacement is the actual distance moved in a specific direction; it is a vector quantity and can be negative.
• Speed is the rate of change of distance without considering direction. It is a scalar quantity.
• Velocity is speed in a given direction, hence it is a vector quantity.
• Acceleration denotes the rate of change of velocity. A resultant force is required to accelerate an object.
• Newton's first law states an object at rest stays at rest and an object in motion remains in motion with same speed and direction unless acted upon by an unbalanced force.
• Newton's second law describes how the velocity of an object changes when it is subjected to an external force.
• Newton's third law states that for every action, there is an equal and opposite reaction.

Fundamentals of Energy

• Energy is the ability to do work or produce heat and cannot be created or destroyed but can change form, according to the law of conservation of energy.
• Kinetic energy is the energy possessed by an object due to its motion.
• Potential energy is the energy that an object possesses because of its position in a force field, such as gravitational force field of the Earth.
• Mechanical energy is the energy that is possessed by an object due to its motion or due to its position.
• Work done is the energy transferred by a force and is calculated as force times the distance in the direction of the force.
• Power quantifies the rate at which work is done or energy is transferred.

Principles of Matter

• Matter is any substance that has mass and takes up space by having volume.
• All matter is composed of atoms, which are the smallest unit that defines the chemical elements.
• Three basic states of matter are solid, liquid and gas.
• The particle model of matter describes the movement and arrangement of particles in solids, liquids and gases.
• Heat plays a significant role in changes of state (e.g., melting, freezing, evaporation, condensation) where energy is transferred.
• Thermal energy is the total potential and kinetic energy of all the microscopic particles in an object.
• Density specifies how much mass is in a given volume. This can cause buoyancy in fluid due to pressure difference.
• Pressure indicates the force exerted per unit area and it increases when temperature or volume is increased in a gas (provided other variables remain constant).