Mechanics Chapter 8

Question 1

Modelling Assumptions:

Particle (2)

Answer 1

Mass of the object is concentrated at a single point

Rotational forces and air resistance can be ignored

Question 2

Modelling Assumptions:

Rod (3)

Answer 2

Mass is concentrated along a line
No thickness
Rigid - does not bend or buckle

Question 3

Modelling Assumptions:

Lamina (1)

Answer 3

Mass is distributed across a flat surface

Question 4

Modelling Assumptions:
Uniform Body (1)

Answer 4

Mass of the object is concentrated at a single point at the geometrical centre of the body - the centre of mass

Question 5

Modelling Assumptions:
Light Object (2)

Answer 5

Treat object as having zero mass

Tension the same at both ends of a light string

Question 6

Modelling Assumptions:
Inextensible string (1)

Answer 6

Acceleration is the same in objects connected by a taut inextensible string

Question 7

Modelling Assumptions:
Smooth Surface (1)

Answer 7

There is no friction between the surface and any object on it

Question 8

Modelling Assumptions:
Rough Surface (1)

Answer 8

Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force

Question 9

Modelling Assumptions:

Wire (1)

Answer 9

Treated as one-dimensional

Question 10

Modelling Assumptions:

Smooth and Light Pulley (2)

Answer 10

Pulley has no mass

Tension is the same on either side of the pulley

Question 11

Modelling Assumptions:

Bead (2)

Answer 11

Moves freely along a wire or string

Tension is the same on either side of the bead

Question 12

Modelling Assumptions:

Peg (2)

Answer 12

Dimensionless and fixed

Can be rough or smooth as specified in question

Question 13

Modelling Assumptions:
Air Resistance (1)

Answer 13

Usually modelled as being negligible

Question 14

Modelling Assumptions:

Gravity (3)

Answer 14

Assume that all objects with mass are attracted towards the Earth
Earth’s gravity is uniform and acts vertically downwards
‘g’ is constant and is taken as 9.8 ms^-2 unless otherwise stated in the question

Question 15

What is a particle?

Answer 15

An object with negligible dimensions

Question 16

What is a rod?

Answer 16

A pole or beam where all dimensions but one are negligible

Question 17

What is a lamina?

Answer 17

An object with area but negligible thickness, like a sheet of paper

Question 18

What is a uniform body?

Answer 18

An object where mass is distributed evenly

Question 19

What is a light object?

Answer 19

An object with mass that is small compared to other masses, like a string or pulley

Question 20

What is an inextensible string?

Answer 20

A string that does not stretch under load

Question 21

What is a rough surface?

Answer 21

A surface that is not smooth

Question 22

What is a wire?

Answer 22

A rigid, thin length of metal

Question 23

What is a bead?

Answer 23

A particle with a hole in it for threading on a wire or string

Question 24

What is a peg?

Answer 24

A support from which a body can be suspended or rested

Question 25

What is air resistance?

Answer 25

Resistance experienced as an object moves through the air

Question 26

What is gravity?

Answer 26

The force of attraction between all objects

Question 27

What is weight?

Answer 27

The gravitational force that acts vertically downwards

Question 28

What is normal reaction?

Answer 28

A force that acts perpendicular to the surface an object is in contact with

Question 29

What is friction?

Answer 29

A force that opposes the motion between two rough surfaces

Question 30

What is tension?

Answer 30

A force acting on an object if a string is pulling it

Question 31

What is thrust/compression?

Answer 31

The force of an object being pushed (e.g. by a light rod)

Question 32

What is buoyancy?

Answer 32

The upward force on an object allowing it to float or rise when submerged

Question 33

What is i?

Answer 33

The horizontal component of a vector

Question 34

What is j?

Answer 34

The vertical component of a vector

Question 35

What are all vectors made up of? (2)

Answer 35

``` Horizontal component (multiple of i) Vertical component (multiple of j) ```

Question 36

How is the magnitude of a vector calculated?

Answer 36

Pythagoras' theorem using the components of a vector

Question 37

What do parallel vectors have in common?

Answer 37

They are multiples of each other