3.4 Mechanics and Materials

Question 1

Acceleration

Answer 1

change in V per unit t

Question 2

Acceleration of free fall

Answer 2

Acceleration of an object only acted on by force of gravity

Question 3

Braking distance

Answer 3

Distance travelled by vehicle in time taken to stop

Question 4

Brittle

Answer 4

Snaps without bending or stretching when subject to stress

Question 5

Centre of mass

Answer 5

Point through which a single force on the body has no turning affect

Question 6

Couple

Answer 6

Pair of equal and opposite forces acting upon the same body but not along the same line

Question 7

denisty

Answer 7

mass per unit volume for substance

Question 8

displacement

Answer 8

distance in a given direction from equilibrium position

Question 9

drag force

Answer 9

force of fluid resistance on an object moving through fluid

Question 10

ductile

Answer 10

stretches easily without breaking

Question 11

efficiency

Answer 11

ratio of useful energy transferred to energy supplied to it output power : input power

Question 12

elastic limit

Answer 12

point beyond which wire is permanently stretched

Question 13

elasticity

Answer 13

property of solid that allows it to regain shape after being deformed

Question 14

equilibrium

Answer 14

State of an object when at rest or in uniform motion

Question 15

friction

Answer 15

force opposing the motion of a surface that moves or tries to move across another surface

Question 16

Hooke’s Law

Answer 16

the extension of a spring is proportional to the force applied to it

Question 17

inertia

Answer 17

resistance of an object to a change of its motion

Question 18

kinetic energy

Answer 18

energy of an object due to its motion

Question 19

mass

Answer 19

measure of inertia of the motion of an object

Question 20

moment

Answer 20

about a point is the force x perpendicular distance from the line of action of the force to the point

Question 21

limit of proportionality

Answer 21

limit beyond which - if a wire or spring is stretched - the extension is no longer proportional to the force applied

Question 22

Newton’s 1st Law of Motion

Answer 22

object remains at rest or in uniform motion unless acted upon by a resultant force

Question 23

Newton’s 2nd Law of Motion

Answer 23

rate of change of momentum of an object is proportional to the resultant force applied to it

Question 24

plastic deformation

Answer 24

deformation of a solid beyond the elastic limit

Question 25

pressure

Answer 25

Force applied per unit area, perpendicular to the surface of an object.

Question 26

conservation of energy

Answer 26

energy cannot be created or destroyed

Question 27

principle of moments

Answer 27

object in equilibrium: sum of clockwise moments = sum of anticlockwise moments about a point

Question 28

rest energy

Answer 28

energy due to rest mass - equal to mc^2

Question 29

scalar

Answer 29

physical quantity with magnitude only

Question 30

speed

Answer 30

change of distance per unit time

Question 31

stiffness constant

Answer 31

force per unit extension needed to extend a wire or spring

Question 32

stopping distance

Answer 32

thinking distance + braking distance

Question 33

stopping potential

Answer 33

minimum pd applied to a metal plate to attract all the photoelectrons emitted from its surface back to the surface

Question 34

strain

Answer 34

extension per unit length of a solid when deformed

Question 35

stress

Answer 35

force per unit area of cross section in a solid perpendicular to cross section

Question 36

useful energy

Answer 36

energy transferred to where it is wanted when its wanted

Question 37

vector

Answer 37

physical quantity with magnitude and direction

Question 38

velocity

Answer 38

change of displacement per unit time

Question 39

weight

Answer 39

force of gravity acting on an object due to its mass

Question 40

work

Answer 40

force x distance moved in the direction of the force

Question 41

yield point

Answer 41

point at which the stress in a wire suddenly drops when the wire is subjected to increasing strain

Question 42

Young’s Modulus

Answer 42

tensile stress (F/A) / tensile strain (∆L/L), assuming limit of proportionality has not been exceeded

Question 43

projectile

Answer 43

projected object in motion acted on only by the force of gravity

Question 44

conservation of momentum

Answer 44

for a system of interacting objects total momentum remains constant provided no external resultant force acts on the system

Question 45

sublimation

Answer 45

change of state when a solid changes directly into a gas

Question 46

elastic collision

Answer 46

total kinetic energy after the collision equals total kinetic energy before the collision