G481 Definitions Flashcards
Displacement is defined as
The distance travelled in a particular direction
Velocity is defined as
The rate of change of displacement with time
A scalar quantity
Has only magnitude
A vector quantity
Has both magnitude and direction
Acceleration is defined as
The rate of change of velocity with time
The gradient of a displacement time graph is equal to
Velocity
The gradient of a velocity time graph is equal to
Acceleration
The area under a velocity time graph is equal to
Displacement
The 4 equations of motion apply only in situations where which 2 conditions are met?
The acceleration is constant
The motion is in a straight line
One Newton is defined as
The force that will give a 1Kg mass an acceleration of 1ms-2 in the direction of the force
Newton’s 1st Law states…
An object will remain at rest or move with constant velocity unless it is acted on by an external force
Newton’s 2nd Law states
If there is a resultant external force on an object it will accelerate in the direction of the external force. The acceleration is directly proportional to the resultant force and inversely proportional to the object’s mass.
or
The rate of change of momentum of an object is directly proportional to the resultant external force applied
The centre of gravity of an object is defined as …
The point through which the entire weight of the object may be considered to act
The moment of a force is defined as…
Force x perpendicular distance of the pivot from the line of action of the force
The principle of moments states that…
For any object that is in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point
The torque of a couple is defined as
one of the forces x perpendicular distance between the forces
Pressure =
Force / Area
Density =
Mass/Volume
Power =
Work done (or energy transferred) / time taken
Seat belts, air bags and crumple zones all improve road safety by…
Increasing the time for the driver to come to a halt. This reduces the rate of momentum change, which in turn leads to reduced impact forces on the driver
Factors which increase braking distance include..
Increased speed
Things which reduce friction between the tyres and the road (tyre condition, road surface, water, ice)
Things which affect brake condition
Factors which increase thinking distance include…
Increased speed
Things which affect the driver’s reaction time (alcohol, drugs, tiredness, medical condition)
A Joule is defined as…
The amount of work done when a force of 1 Newton moves a distance of 1 metre in the direction of the force
The principle of energy conservation states that…
For a closed system, energy can be transformed to other forms but the total amount of energy remains constant
Hooke’s Law states that…
The extension of a material is directly proportional to the applied force providing the elastic limit is not exceeded
Stress is defined as
The force applied per unit CSA of the material
Strain is defined as
The fractional increase in the length of the material
The ratio of stress to strain for a material is called
The Young Modulus (stiffness) of the material
Brittle materials
Break at the elastic limit
Ductile materials
Show plastic deformation beyond the elastic limit
Elastic behaviour means …
An object returns to its original length and shape when the force is removed
The strength of a material tells us…
How much stress is needed to break a material.
The maximum stress a material can withstand is called
Ultimate Tensile Strength (UTS)
The elastic potential energy stored in a stretched material is given by
The area under the force extension curve for the material (provided the elastic limit has not been exceeded)
