AS FEM Definitions

Question 1

Explain the term systematic error

Answer 1

Systematic errors in measurements are errors which show

A pattern
A bias
Or a trend

Question 2

State what is meant by a scalar quantity

Answer 2

A scalar quantity is a quantity that has magnitude only

Question 3

State two examples of scalar quantities

Met

Answer 3

Mass
Energy
Temperature

Question 4

State example of a vector quantity ( other than force )

Answer 4

Velocity
Acceleration
Momentum

Question 5

State the difference between a scalar quantity and a vector quantity

Answer 5

A vector quantity has direction (as well as magnitude) and a scalar quantity does not

Question 6

Explain what is meant by the spring constant k of a spring

Answer 6

K= force/ extension

Question 7

State the principle of moments

Answer 7

For a system in equilibrium, the sum of the ACW moments = sum of CW moments

About any given point

Question 8

State the principle of

Conservation of momentum

Answer 8

The resultant momentum of a system is constant before and after a collision, provided no external forces act

The total momentum of a system is the same before and after an interaction in an isolated system

Question 9

State 2 relationships between the forces that must be satisfied

if an object is to remain in equilibrium

Answer 9

The resultant force acting on an object = 0

And

The CW and ACE moments must be equal, or the resultant torque is 0

Question 10

Define the moment of a force

Answer 10

The product of

The force

And

The perpendicular distance from the line of action of the force to the pivot

Question 11

Explain what is meant by the centre of gravity

Answer 11

The point (in a body) at which the weight (or gravitational force) of an object appears to act

Question 12

State 2 conditions that must be satisfied for the rod to be in equilibrium

Answer 12

Resultant force =0
And
Resultant torque = 0 at any point

Question 13

What is meant by

tensile stress

Answer 13

Tension\ area

Or

Force/ area (perpendicular to the surface at which the force acts)

Question 14

Tensile strain

Answer 14

Extension / original length

Question 15

Elastic limit

Answer 15

The point, stress, strain, force/ extension up to which

Either - all energy sustained to stretch is returned when the deformed force is removed

Or- the shape returns to its original form when the deforming force is removed

Or- beyond such strength causes plastic deformation or permanent deformation

Question 16

Yield stress of a material

Answer 16

The force per unit area

At which a material is extended

Considerably, a lot, plastically

Question 17

Define the young modulus for a material

Answer 17

Young modulus=

Tensile stress/ tensile strain

Question 18

Define the density of a material

Answer 18

Density =

Volume

Question 19

State hooke’s law for a material in the form of a wire

Answer 19

The extension is proportional to the applied force up to the limit of proportionality

Question 20

Define young modulus of a material with units it is measured in

(2)

Answer 20

Ratio of tensile stress to tensile strain

Pa

/

Nm -2

Question 21

Constant k of a spring

And unit of k

Answer 21

K= force/ extension

Measured in Nm -1

Question 22

State the formula for principle of conservation of momentum

Answer 22

E mv = 0

Where mv is momentum

E as in sum of

Question 23

Inelastic collision

Answer 23

Kinetic energy is not conserved

Question 24

How the force acting on a body

Is related to the change in momentum of the body

Answer 24

Force= rate of change of momentum

Question 25

Newton’s first law of motion

Answer 25

Objects either stay at rest or moves with constant velocity unless acted on by a force

Question 26

Ratio of acceleration force to weight

Answer 26

F over mg