Mechanics and Materials

Question 1

Vector

Answer 1

Any physical quantity that has a direction as well as a magnitude.

Question 2

Scalar

Answer 2

Any physical quantity that is not directional.

Question 3

Equilibrium

Answer 3

Forces are balanced, at rest or moving at a constant velocity.

Question 4

The moment of a force

Answer 4

F x d = force x the perpendicular distance from the pivot. Units (Nm).

Question 5

The principle of moments

Answer 5

The sum of the clockwise moments = the sum of the anticlockwise moments.

Question 6

The centre of mass

Answer 6

The point of a body through which a single force on the body has no turning effect.

Question 7

Uniform

Answer 7

The centre of mass is exactly at the centre of the body.

Question 8

A couple

Answer 8

A pair of equal and opposite forces acting on a body, but not along the same line.

Question 9

Displacement

Answer 9

Distance in a given direction.

Question 10

Speed

Answer 10

Change of distance per unit time.

Question 11

Velocity

Answer 11

Change of displacement per unit time.

Question 12

Acceleration

Answer 12

Change of velocity per unit time.

Question 13

Suvat equation excluding s

Answer 13

v = u + at

Question 14

Suvat equation excluding a

Answer 14

s = (u + v) t / 2

Question 15

Suvat equation excluding v

Answer 15

s = ut + 1/2 at^2

Question 16

Suvat equation excluding t

Answer 16

v^2 = u^2 + 2as

Question 17

Projectile

Answer 17

Any object acted upon only by the force of gravity. The acceleration of the object is always equal to g, no horizontal component to the acceleration so the horizontal velocity is constant. Motions in the horizontal and vertical directions are independent of each other.

Question 18

Newton’s first law of motion

Answer 18

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

Question 19

Newton’s second law of motion

Answer 19

F = ma

Question 20

Weight

Answer 20

W = mg

Question 21

Inertia

Answer 21

The resistance to change of motion. Mass is a measurement of inertia.

Question 22

Drag force

Answer 22

Experienced by any object moving through a fluid.

Question 23

Terminal speed

Answer 23

As drag force increases, resultant force equals zero. Zero acceleration and constant velocity.

Question 24

Thinking distance

Answer 24

The distance travelled by a vehicle in the time it takes the driver to react.

Question 25

Braking distance

Answer 25

The distance travelled by a car in the time it takes to stop safely, from when the brakes were first applied.

Question 26

Stopping distance

Answer 26

Thinking distance + braking distance

Question 27

Momentum, p

Answer 27

Mass x velocity

Question 28

Impulse / change of momentum

Answer 28

Force x time

Question 29

Newton’s third law of motion

Answer 29

When two objects interact, they exert equal and opposite forces on each other.

Question 30

The principle of conservation of momentum

Answer 30

For a system of interacting objects, the total momentum remains constant, provided no external resultant forces act on the system.

Question 31

Elastic collision

Answer 31

One where there is no loss of kinetic energy.

Question 32

Inelastic collision

Answer 32

Occurs when the colliding objects have less kinetic energy after the collision than before the collision.

Question 33

Principle of conservation of energy

Answer 33

Energy cannot be created or destroyed.

Question 34

Work done

Answer 34

Force x distance moved in the direction of the force

Question 35

Kinetic energy

Answer 35

Ek = 1/2 m v^2

Question 36

Change of gravitational potential energy

Answer 36

ΔEp = m g Δh

Question 37

Definition of power

Answer 37

The rate of transfer of energy.

Question 38

Power equations

Answer 38

P = ΔE /Δt = ΔW /Δt

Question 39

Density of a substance

Answer 39

Mass per unit volume.

Question 40

Hooke’s law definition

Answer 40

The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length.

Question 41

Hooke’s law equation

Answer 41

F = k ΔL, where k is the spring constant.

Question 42

Elasticity of a solid material

Answer 42

Its ability to regain its shape after it has been deformed or distorted and the forces that deformed it have been released.

Question 43

Tensile deformation

Answer 43

Deformation that stretches an object.

Question 44

Compressive deformation

Answer 44

Deformation that compresses an object.

Question 45

Tensile stress

Answer 45

Tension / Area

Question 46

Unit of stress

Answer 46

Pascal (Pa) equal to 1 N m^-2

Question 47

Tensile strain

Answer 47

ΔL /L

Question 48

Young modulus

Answer 48

Tensile stress / Tensile strain

Question 49

Elastic limit

Answer 49

The point beyond which the wire is permanently stretched and suffers plastic deformation.

Question 50

Brittle material

Answer 50

Snaps without any noticeable yield.

Question 51

Ductile material

Answer 51

Can be drawn into a wire.

Question 52

Elastic energy stored in a stretched wire

Answer 52

1/2 T ΔL

Question 53

μ

Answer 53

μ = density x cross sectional area = weight/unit length.