topic 1 forces and motion

• newtons third law states for every action, there is an equal but opposite reaction. this means that all forces come in Pairs. within these pairs, two forces have equal size but they act on different bodies In opposite direction
• stability, the lower the centre of gravity is the more stable the object. the centre of gravity must remain over the base to remain stable and not topple
• a moment is the turning effect of a force, moments act about a point (Pivot) in a clockwise or anticlockwise direction
• principles of movement, if an object is balanced the total clockwise moment about a pivot equals the Total anticlockwise moment about that pivot, f1 x d1 = f2 x d2
• moment equation, moment = force x distance perpendicular to turning force
• centre of gravity is a point from which the weight of a body or system may be considered to act. gravity is concentrated at this point, all force of gravity is exerted
• forces, is push, pull, stretch, lift, throw applied to an object. it can change the speed, shape or direction of an object. there are contact and non contact forces. it is a vector quantity as it has a direction
• force equation, force = mass x acceleration. force is measured in N. mass is measured in kg. acceleration is measured in ms
• the velocity of an object is the speed of an object in a given direction, it is a vector quantity
• average speed equation, average speed = distance travelled divided by time taken. distance is measured in m. time take is measured in s. speed is measured in ms
• speed is a measure of how far an object moves in a given time, it is a scalar quantity so no direction is involved, it is measured in ms
• magnetic force is force cause by a magnetic field, non contact
• weight equation, weight = mass x gravitational field strength
• elastic force is force related in stretching and compressing an object, contact
• tension is force applied to hang an object, contact
• air resistance is force due to contact between an object and air, contact
• weight equation, weight = mass x 10, the unit is newton's per kilogram
• weight is force due to gravity, non contact
• newtons 2nd law states the acceleration of an object is proportional to the resultant force of an object and inversely proportional to the mass of the object
• factors affecting vehicle stopping distance include, driver tiredness, phone distractions, poor visibility, level of tire inflation, car conditions such as poor brakes, speed
• buoyancy is force caused by the pressure of water, contact
• scalar quantity has only magnitude and no direction, examples include speed, distance, mass, energy, temperature and time
• displacement is a vector quantity that gives the net distance from start to finish with a direction, measured in m
• friction is the force due to contact between two surfaces, contact, it always acts against the direction of motion
• forces that act along a line, subtract the magnitude of the smaller force away from the magnitude of the larger force. the direction of the resultant force is the same as the direction of the larger force
• resultant force is the sum of all forces acting on an object, if the resultant force is not 0 the forces on the object are said to be unbalanced, the object will therefore change velocity this can be a change in speed, direction or both
• vector quantity has a magnitude and direction, examples include force, velocity, displacement, weight, acceleration and momentum
• distance is how far an object moves it is a scalar quantity so does not involve direction. measured in m
• stopping distance equation, stopping distance = thinking distance + braking distance
• electrostatic force, force exerted by a charged particle or a charged object, non contact
• terminal velocity is as it gains speed objects weight stays the same but the air resistance on it increases. there is a resultant force acting downwards, eventually the objects weight is balanced by the drag/air resistance. there is no resultant force and the object reaches a steady speed called terminal velocity. drag upwards, weight downwards
• hookes law the extension of a spring is directly proportional to the force applied until it reaches its elastic limit or proportional is not exceeded, stiffer the spring higher the spring constant
• extension of spring equation, extension of spring = stretch length x final length
• force, spring constant equation - force = spring constant x extension
• acceleration equation, acceleration equals change in velocity divided by change in time. acceleration is measured in ms2 velocity is measured in ms time is measured in s
• if an object speed up, velocity increases and the acceleration is positive. if an object slows down, velocity decreases and the acceleration is negative, deceleration
• velocity time graph, the line is the gradient, flat sections are steady speed, stepper means accelerating or decelerating, curve means changing acceleration
• distance time graphs, flat sections means stopped, steeper means faster, curves mean acceleration, levelling off curve means deceleration, speed = change in vertical divided by change in horizontal
• final speed 2 equation, final speed 2 = initial speed 2 + (2 x acceleration x distance moved)
• momentum equation, momentum = mass x velocity