Definitions Flashcards
Acceleration
the rate of change of velocity
average speed
the distance travelled over time for the entire region of interest
Braking distance
the distance travelled between the the brakes being applied and the vehicle coming to a stop. It is affected by the vehicle and road conditions
Displacement
the direct distance between an object’s starting position and its ending position. It is a vector quantity and has both magnitude and direction
Explain what is meant by the term Free fall
An object is said to be in free fall when the only force acting on it is the force of gravity
instantaneous speed
the exact speed of the object at a specific given point
Explain what is meant by the term projectile motion
the motion of an object that is fired from a point and then upon which only gravity acts
reaction time
the time taken to process a stimulus and trigger a response to it. It is affected by alcohol, drugs, and tiredness
stopping distance
the sum of thinking distance and braking distance for a driven vehicle
thinking distance
the distance travelled in the time it takes for the driver to react. It is affected by alcohol, drugs, and tiredness
velocity
the rate of change in displacement. It is a vector quantity so has both magnitude and direction
Archimedes principle
the upward force experienced by an object fully or partially submerged in a liquid is equal to the weight of the fluid it displaces
center of gravity
the single point through which object’s weight can be said to act
center of gravity
the single point through which object’s weight can be said to act
center of mass
the single point through which all the mass of the object can be said to act
couple
two parallel and equal forces that act on an object through different lines of action. it has the effect of causing rotation without translation.
drag
the frictional force that an object experiences when moving through a fluid
equillibrium
for an object to be in equilibrium, the resultant force and the resultant moment is to be zero
friction
the resistive force that is produced when there is a relative movement between two surfaces
moment of a force
the product of a force and the perpendicular distance to the line of action from the force to the pivot
moment of a force
the product of a force and the perpendicular distance from the line of action from the force to the pivot
Newton 2nd law
the sum of the forces acting on an object is equal to the rate of change of momentum. It is also expressed as the net force acting on object is equal to the product of the object’s mass and acceleration
normal contact force
the reaction force between an object and surface
Principle of Moments
For an object to be in equilibrium, the sum of the clockwise moments acting about a point must be equal to the sum of the anticlockwise moments acting about the same point.
Tension
The result of two forces acting on an object in opposite, outwards directions.
Terminal Velocity
The maximum velocity of an object that occurs when the resistive and driving forces acting on the object are equal to each other.
Weight
The product of an object’s mass and the gravitational field strength at its location.
Conservation of Energy
In a closed system with no external forces the total energy of the system before an event is equal to the total energy of the system after the event.
Efficiency
The useful output (e.g. power, energy) of a system divided by the total output.
Gravitational Potential Energy
The energy gained by an object when it is raised by a height in a gravitational field.
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.
Power
The work done or energy transferred by a system divided by the time taken for that to be done.
Brittle
A brittle object is one that shows very little strain before reaching its breaking stress.
Compression
The result of two coplanar forces acting into an object. Compression usually results in a reduction in the length of the object.
Compressive Deformation
The changing of an object’s shape due to compressive forces.
Ductile
A material is ductile if it can undergo very large extensions without failure. Ductile materials can be stretched into wires.
Elastic Deformation
If a material deforms with elastic behaviour, it will return to its original shape when the deforming forces are removed. The object will not be permanently deformed.
Elastic Potential Energy
The energy stored in an object when it is stretched. It is equal to the work done to stretch the object and can be determined from the area under a force-extension graph.
Extension
The increase of an object’s length.
Hooke’s Law
The extension of an elastic object will be directly proportional to the force applied to it up to the object’s limit of proportionality.
Plastic Deformation
If a material deforms with plastic behaviour, it will not return to its original shape when the deforming forces are removed. The object will be permanently deformed.
Polymeric
A material made from polymers.
Spring Constant
The constant of proportionality for the extension of a spring under a force. The higher the spring constant, the greater the force needed to achieve a given extension.
Strain
The ratio of an object’s extension to its original length. It is a ratio of two lengths and so has no unit.
Stress
The amount of force acting per unit area. Its unit is the Pascal (Pa).
Tensile Deformation
The changing of an object’s shape due to tensile forces.
Ultimate Tensile Strength
The maximum stress than an object can withstand before fracture occurs.
Young Modulus
The ratio of stress to strain for a given material. Its unit is the Pascal (Pa).
Conservation of Momentum
The total momentum of a system before an event must be equal to the total momentum of the system after the event, assuming no external forces act.
Elastic Collisions
A collision in which the total kinetic energy of the system before the collision is equal to the total kinetic energy of the system after the collision.
Impulse:
The change of momentum of an object when a force acts on it. It is equal to the product of the force acting on the object and the length of time over which it acts.
Inelastic Collisions
A collision in which the total kinetic energy of the system before the collision is not equal to the kinetic energy of the system after the collision.
Linear Momentum
The product of an object’s mass and linear velocity.
Newton’s First Law
An object will remain in its current state of motion, unless acted on by a resultant force. An object requires a resultant force to be able to accelerate.
Newton’s Second Law
The sum of the forces acting on an object is equal to the rate of change of momentum of the object.
Newton’s Third Law
Every action has an equal and opposite reaction. If an object exerts a force on another object, then the other object must exert a force back, that is opposite in direction and equal in magnitude.
