Year 12 - Mechanics Flashcards
Acceleration
The rate of change of velocity with respect to time.
Centre of Gravity
The point on an object through which the entire weight of the object may be considered to act.
Centre of Mass
The point at which a (resultant) force directed through an object will not give it a moment / will not cause the object to rotate.
Conservation of Energy
Theprinciple of conservation of energystates that energy cannot be created or destroyed in any process. It can only be transferred.
Conservation of Momentum
The total momentum of a system of objects remains constant E.g. Momentum before (a collision) = momentum after (a collision), provided no resultant external force acts on the system (in a closed system).
Couple
Consists of two equal and opposite forces.
Displacement
The distance between the start point and end point in a straight line. Displacement is a vector quantity.
Efficiency
Efficiency isa measure of how efficiently a system transfers energy. It is calculated by dividing the useful energy/power output by the total energy/power input.
Elastic Collision
Kinetic Energy is conserved.
Friction
A force that opposes motion.
Gravitational Potential Energy (GPE)
Gravitational Potential Energyis defined as the amount of work done in order to raise a body through a vertical height h.
Impulse
Change in Momentum. Area under a Force - Time Curve.
Inelastic Collision
Kinetic Energy is not conserved.
Moment
The product of the force and the perpendicular distance between the pivot and the line of action of the force.
Momentum
Momentum isthe product of the mass and velocity of a body. Momentum is a vector quantity.
Newton’s First Law
A body will continue in its state of rest or uniform motion in a straight line unless an external resultant force acts on it.
Newton’s Second Law
The rate of change of momentum of a body is proportional to the resultant force acting on it and the change takes place in the direction of the force.
Newton’s Third Law
If body A exerts a force on body B, then body B exerts a force of equal magnitude but in the opposite direction on body A.
Normal Contact Force (Reaction Force)
The forceperpendicular to the surface experienced by a body when it is in physical contact with that surface.
Power
The rate of work done or energy transferred per unit time.
Pressure
The force acting per unit area.
Principle of moments
Sum of /total clockwise moments = sum of/total anticlockwise moments, for a body in equilibrium.
Scalar
A quantity with magnitude only. It does not have direction e.g. Energy.
Speed
The rate of change of distance travelled with respect to time.
Terminal Velocity/Speed
The maximum velocity/speed of a body. It occurs when the resistive and driving forces acting on the body are equal to each other. The forces need to be balanced.
Vector
A quantity that has magnitude and direction e.g. Force.
Velocity
The rate of change of displacement with respect to time.
Work Done
The mechanical transfer of energy to a system or from a system by an external force on it.
