4. Mechanics And Materials Definitions Flashcards

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1
Q

Define breaking stress

A

The maximum stress that an object can withstand before failure occurs

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2
Q

Define brittle

A

A brittle object will show very little strain before reaching its breaking point

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3
Q

Define centre of mass

A

The single point though which all the mass of an object can be said to act

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4
Q

Define conservation of energy

A

Energy cannot be created or destroyed- it can only be transferred into different forms

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5
Q

Define conservation of momentum

A

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.

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6
Q

Define couple

A

Two equal and opposite parallel force that act on object through different lines of action. It has the effect of causing a rotation without translation.

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7
Q

Define density

A

The mass per unit volume of a material

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8
Q

Define efficiency

A

The ratio of useful output to total input for a given system

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9
Q

Define elastic behaviour

A

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.

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10
Q

Define elastic collision

A

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

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11
Q

Define elastic limit

A

The force beyond which an object will no longer deform elastically and instead deform plastically. Beyond the elastic limit, when the deforming forces are removed, the object will not return to its original shape.

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12
Q

Define elastic strain energy

A

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.

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13
Q

Define equilibrium

A

For an object to be in equilibrium, both the resulting force and resultant moment acting on the object must be equal to zero.

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14
Q

Define Hooke’s Law

A

The extension of an elastic object will be directly proportional to the force applied to it up to the object’s limit of proportionality

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15
Q

Define impulse

A

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

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16
Q

Define inelastic collision

A

A collision in which the total kinetic energy is the system before the collision is not equal to the kinetic energy of the system after the collision

17
Q

Define moment

A

The product of a force and the perpendicular distance from the line of action of the force to the pivot

18
Q

Define momentum

A

The product of an object’s mass and velocity

19
Q

Define Newton’s first law

A

An object will remain it its current state of motion, unless acted on by a resultant force. An object requires a resultant force to be able to accelerate

20
Q

Define Newton’s second law

A

The sum of the forces acting on an object is equal to the rate of change of momentum of the object

21
Q

Define Newton’s third law

A

Every action has an equal and opposite reaction. If an object exerts a force on another object, the the other object must extend a force back, that is opposite in direction and equal in magnitude.

22
Q

Define plastic behaviour

A

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.

23
Q

Define the principle of moments

A

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 point.

24
Q

Define scalar

A

A scalar quantity is one that only has a magnitude. Examples include length, mass and temperature.

25
Q

Define spring constant

A

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.

26
Q

Define stiffness

A

A measure of how difficult it is to stretch a given object

27
Q

Define tensile strength

A

The ratio of an object’s extension to its original length. It is a ratio of two lengths and so has no unit.

28
Q

Define tensile stress

A

The amount of force acting per unit area. Its unit it the pascal (Pa)

29
Q

Define terminal speed

A

The maximum speed of an object that occurs when the resistive and driving forces acting on the object are equal to each other.

30
Q

Define vector

A

A vector quantity is one that has both a magnitude and a direction. Examples include velocity, displacement and acceleration.

31
Q

Define Young modulus

A

The ratio of stress to strain for a given material. Its unit is the Pascal (Pa).