Motion, forces and energy

• a scalar quantity has magnitude only
• a vector quantity has magnitude and direction
• scalar quantities: distance, speed, time, mass, energy and temperature
• vector quantities: force, weight, velocity, acceleration, momentum, electric field strength and gravitational field strength
• speed is distance travelled per unit time
• velocity is speed in a given direction
• the acceleration of free fall g for an object near to the surface of the Earth is approximately constant
• acceleration is change in velocity per unit time
• a deceleration is a negative acceleration
• mass is a measure of the quantity of matter in an object at rest relative to the observer
• weight is a gravitational force on an object that has mass
• gravitational field strength is force per unit mass
• weights (and masses) may be compared using a balance
• density is mass per unit volume
• forces may produce changes in the size and shape of an object
• the spring constant is force per unit extension
• the force and the acceleration are in the same direction
• an object either remains at rest or continues in a straight line at constant speed unless acted on by a resultant force
• a resultant force may change the velocity of an object by changing its direction of motion or its speed
• Describe the motion in a circular path due to a force perpendicular to the motion as: (a) speed increases if force increases, with mass and radius constant (b) radius decreases if force increases, with mass and speed constant (c) an increased mass requires an increased force to keep speed and radius constant
• Describe the motion in a circular path due to a force perpendicular to the motion as: (a) speed increases if force increases, with mass and radius constant (b) radius decreases if force increases, with mass and speed constant (c) an increased mass requires an increased force to keep speed and radius constant
• Describe the motion in a circular path due to a force perpendicular to the motion as: (a) speed increases if force increases, with mass and radius constant (b) radius decreases if force increases, with mass and speed constant (c) an increased mass requires an increased force to keep speed and radius constant
• solid friction is the force between two surfaces that may impede motion and produce heating
• friction (drag) acts on an object moving through a liquid
• friction (drag) acts on an object moving through a gas (e.g. air resistance)
• the moment of a force is a measure of its turning effect
• the moment of a force as moment = force × perpendicular distance from the pivot
• when there is no resultant force and no resultant moment, an object is in equilibrium
• momentum is mass × velocity
• impulse is force × time for which force acts
• resultant force is the change in momentum per unit time
• energy may be stored as kinetic, gravitational potential, chemical, elastic (strain), nuclear, electrostatic and internal (thermal)
• mechanical or electrical work done is equal to the energy transferred
• radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal
• energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy
• energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy
• energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy
• energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy
• energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy
• energy may be obtained, or electrical power generated, from: (a) chemical energy stored in fossil fuels (b) chemical energy stored in biofuels (c) water, including the energy stored in waves, in tides, and in water behind hydroelectric dams (d) geothermal resources (e) nuclear fuel (f) light from the Sun to generate electrical power (solar cells) (g) infrared and other electromagnetic waves from the Sun to heat water (solar panels) and be the source of wind energy