U1 definitions

Question 1

Resultant force

Answer 1

sum of all forces

Question 2

Equilibrium

Answer 2

no resultant force, no moment

Question 3

Principle of moments

Answer 3

a body will be in equilibrium if the sum of clockwise moments acting on it is equal to the sum of the anticlockwise moments

Question 4

Gravitational field strength

Answer 4

the force per unit mass

Question 5

Center of gravity

Answer 5

the point which weight of an object is considered to act

Question 6

Newton’s first law

Answer 6

an object will remain at rest or in state of uniform motion until acted upon by a resultant force

Question 7

Newton’s second law

Answer 7

F=ma

Question 8

Newton’s third law

Answer 8

for every action, there are equal and opposite forces (same type of forces)

Question 9

Conservation of energy

Answer 9

energy cannot be created or destroyed

Question 10

Conservation of momentum

Answer 10

In a closed system, sum of momentum before is equal to the sum of momentum after

Question 11

Hooke’s law

Answer 11

the force needed to extend a spring is proportional to the extension of the spring

Question 12

Young modulus

Answer 12

stress per unit strain

Question 13

Elastic deformation

Answer 13

when force is removed, it returns to its original size and shape

Question 14

Plastic deformation

Answer 14

when force is removed, it cannot return to its original size and shape

Question 15

Elastic limit

Answer 15

stress beyond which it does not return to its original shape when the force is removed

Question 16

Limit of proportionality

Answer 16

point beyond which Hooke’s law no longer applies

Question 17

Yield point

Answer 17

beyond this point, there is little or no increase in stress required to produce large extension

Question 18

Ultimate tensile stress

Answer 18

highest stress within the material

Question 19

Tensile stress

Answer 19

stress at which material will break

Question 20

Breaking stress

Answer 20

material breaks at this point

Question 21

Hardness

Answer 21

resistance to scratching

Question 22

Strength

Answer 22

stress needed to break

Question 23

Strong

Answer 23

requires a large stress to break

Question 24

Tough

Answer 24

absorb a large amount of energy per volume before fracture

Question 25

Ductile

Answer 25

pull into shape

Question 26

Malleable

Answer 26

compress into shape

Question 27

Laminar flow

Answer 27

layers of fluid flow past each other without mixing

Question 28

Terminal velocity

Answer 28

constant maximum velocity reached by an object falling through a fluid when resultant force equals to zero

Question 29

Upthrust

Answer 29

weight of fluid displaced by object