mechanics Flashcards
(22 cards)
Centre of Mass
The average point of all parts of an object weighted according to their
mass. It is the point through which the total mass of the object is said to act.
Conservation of Energy
In a closed system with no external forces the energy of the
system before an event is equal to the energy of the system after the event. The energy does
not need to be in the same form after the event as it was before the event.
Momentum
The product of an objects mass and velocity
Drag
The resistance against the motion of an object through a fluid. It is usually proportional
to the speed of the object
Efficiency
The useful output (e.g. power, energy) of a system divided by the total output
(output/input)
Elastic collision
When the kinetic energy of a system before an event is equal to the
kinetic energy of the system after the event.
Equilibrium
An object is at equilibrium when the moments on it about a point are balanced
and the resultant force on the object is zero
Force
The rate of change of momentum of an object. The product of the object’s mass with
its acceleration
Gravitational Potential Energy
The energy gained by an object when it is raised by a
height in a gravitational field.
Impulse
The change of momentum of an object when a force acts on it. Equal to the area
underneath a force-time graph.
Δp=FxΔt
Inelastic Collision
When the kinetic energy of a system before an event is not equal to the
kinetic energy of the system after the event. The kinetic energy has been transferred to other
forms.
Kinetic energy
The energy an object has due to its motion. It is the amount of energy that
would be transferred from the object when it decelerates to rest
Moment
The product of a force and the perpendicular distance from the line of action to the
pivot about which the force is acting.
Newton’s first law
An object at a constant velocity will remain at a constant velocity
unless acted on by a resultant force. (If this constant velocity is zero the object is at rest
Newton’s second law
If an object is acted upon by a resultant force it will accelerate. The
acceleration is inversely proportional to the mass of the object and directly proportional to the
force acting upon it.
F=MA
Newton’s third law
Every action has an equal and opposite reaction. If an object A exerts
a force on object B, object B will exert a force of equal magnitude but of opposite direction on
object A.
Power
The work done by a system divided by the time taken for that work to be done
Scalar
A quantity with only magnitude and no direction (e.g. mass, energy, length).
Terminal velocity
The maximum velocity an object can achieve. It is the point at which
frictional forces and driving forces are balanced and so no acceleration occurs and the
resultant force on the object is 0 N.
Vector
A quantity with magnitude and direction (e.g. velocity, acceleration, force)
Weight
The force of gravity on an object, the product of the object’s mass and the
acceleration due to gravity
Work done
A force applied over a distance, it is the energy transferred in that distance.
