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# Mechanics Concepts (v17)

last edited by 6 years, 4 months ago
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 Concept L1 Mechanics Concepts Level 2 University Acceleration change in speed over time, whether speeding up or slowing down Change in velocity (not speed!) over time Air Resistance friction acting on an object moving through air Average Speed the total distance traveled divided by the time required to travel that distance Balanced Forces when two forces combine to cancel each other out Centripetal Acceleration Acceleration acting on an object moving around a circle and directed toward the centre of the movement. Centripetal Force Force acting on an object moving around a circle at constant speed (but at the direction of movement changed) Change in Momentum in One Dimension Momentum is changed under the influence of a force acting along the movement of an object, in the same or opposite direction Circular Motion Movement around a circle (at constant speed with one force only providing centripetal force) Conservation of energy (energy) cannot be created or destroyed The total energy before the work is done equals the total of all the forms of energy produced afterwards. Conservation of Momentum in One Direction Total momentum of two or more objects before and after collision (explosion) is the same / equals. Constant Speed speed is not increasing or decreasing but remain consistent over time Constant unchanging Contact Area amount of area shared by two objects e.g. ice skates have sharp edges, and thus a small area in contact with the ice Deceleration decrease in the speed over time of an object Displacement Distance in vector form, when direction of movement is important Distance how far an object has traveled (usually horizontal) Drag or an object moving through air, friction is called "air resistance" or "drag kinetic energy; the kind of energy possessed by moving objects gravitational potential energy; energy possessed by objects that have been lifted up Elastic Collision Collision involving no loss of kinetic energy due to no change in shape of objects. Elastic Potential Energy Energy stored in an extended or compressed spring Energy Gained Energy accumulated at Energy Transfer, e.g. transfer of Kinetic Energy to Potential Energy at ROPE CLIMBING Energy Loss Energy scattered on friction or Air Resistance at Energy Transfer Energy Transfer Transformation between different kinds of energy Equilibrium State of an object at rest or moving uniformly. Condition: both the resultant force is zero and the sum of all the torques acting on a object is zero. Final Velocity Velocity at the end of movement (considered / measured) Force a push or pull that can change an object’s movement Force Components Projections of force on selected directions Free Fall falling motion caused by gravity alone Friction friction is an opposing force; it acts in the opposite direction to a force which is applied to an object g acceleration caused by the earth’s mass (approx. 10 ms-2) Gradient slope of a graph (rise/run) Gravitational Potential Energy Change of position of an object in the Earth's gravitational field. Gravity the force of attraction between any two objects; the Earth is very big and so has a large gravity pulling everything down towards it Height distance (vertical) Impulse Change of Momentum under the influence of force F acting over the period of time Δt. Inelastic Collision Collision involving loss of kinetic energy due to change in shape and/or temperature of objects. Initial Velocity Velocity at the beginning of movement (considered / measured) Instantaneous at an instant of time Instantaneous Speed speed at a particular instant in time Kinetic Energy Energy of a moving object Mass amount of matter in an object or substance Mechanical Energy kinetic or potential (or heat) energy Momentum (p) "quantity of motion" proportional to the velocity and mass of an object Net Force the single force that represents all the forces acting on a body; overall force Power (P), W the rate that energy is changed from one type to another; power is the energy changed divided by the time it takes for the energy to change The rate at which work is done Pressure a measure of the force exerted on a certain area of surface; force per unit area Projectile Motion Motion of a projectile, an object moving through the air without its own source of power, only under the influence of gravity Reaction An equal and opposite force exerted by a body against a force acting upon it Relationship information that can be used to link two things together e.g. force and acceleration Resultant Force a stationary object remains stationary if the sum of the forces acting upon it - resultant force - is zero. A moving object with a zero resultant force keeps moving at the same speed and in the same direction. If the resultant force acting on an object is not zero, a stationary object begins to accelerate in the same direction as the resultant force. Speed how fast an object is traveling; units are distance time-1, e.g. ms-1 Speed-time graphs Graph showing change of speed with time Sprint Constant Slope of the graph of the Force applied to a spring against the extra distance extended. Spring length in equilibrium (natural length) is not included. Stationary stopped, not moving or “at rest” Time ??? Thrust to push or drive with force Torque Turning effect about a pivot under the influence of a force. Can be clockwise or anticlockwise. Same as moment and leverage Unbalanced Forces forces that are NOT balanced; situation leading to acceleration or deceleration of an object Same Vector Addition of Forces Velocity speed (Note: velocity is really the measurement of the rate and direction of motion but at Level 1 Science we treat speed and velocity as the same thing) Velocity Vector Components Horizontal (v cos θ) and vertical (v sin θ) components Weight (Force) the force on an object caused by gravity Work (W), J energy required to make an object move Process of energy transfer from one form to another. Work Done Whenever 'work' is done energy is transferred from one place to another.