Key terminology physics

Question 1

What does it mean if we refer to an object as a particle?

Answer 1

it means the dimensions of the object are negligible

Question 2

What are modelling assumptions when referring to an object as a particle?

Answer 2

• mass of the object is concentrated at a single point
• rotational forces and air resistance can be ignored

Question 3

What does it mean if we refer to an object as a rod?

Answer 3

it means all dimensions but one are negligible, like a pole or beam

Question 4

What are modelling assumptions when referring to an object as a rod?

Answer 4

• mass is concentrated long a line
• no thickness
• rigid (does not ben or buckle)

Question 5

What does it mean if we refer to an object as a lamina?

Answer 5

it means an object with area but negligible thickness like a piece of paper

Question 6

What are modelling assumptions when referring to an object as a lamina?

Answer 6

• mass is distributed across a flat surface

Question 7

What does it mean if we refer to an object as a uniform body?

Answer 7

it means the mass is distributed evenly

Question 8

What are modelling assumptions when referring to an object as a uniform body?

Answer 8

• the mass of the object is concentrated at a single point at he geometrical centre of the body (the centre of mass)

Question 9

What does it mean if we refer to an object as a light object?

Answer 9

mass of the object is small compared to other masses, like a string or a pulley

Question 10

What are modelling assumptions when referring to an object as a light object?

Answer 10

• treat objects as having zero mass
• tension the same at both ends of a light string

Question 11

What does it mean if we refer to an object as a inextensible string?

Answer 11

it means a string that doesn’t stretch under load

Question 12

What are modelling assumptions when referring to an object as an inextensible string?

Answer 12

• acceleration is the same in objects connected by taut inextensible string

Question 13

A smooth surface?

Answer 13

assume that here is no friction between the surface and any object on it

Question 14

A rough surface?

Answer 14

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

Question 15

What does it mean if we refer to an object as a wire?

Answer 15

rigid thin length of metal so is treated to be one -dimensional

Question 16

What does it mean if we refer to an object as a smooth and light pulley?

Answer 16

(this will be all pulleys)
- the pulley has no mass
- tension is the same on either side of the pulley

Question 17

What does it mean if we refer to an object as a bead? assumptions?

Answer 17

• a particle with a whole in it for threading
• moves freely along a wire or string
• tension is the same on either side of the bead

Question 18

What does it mean if we refer to an object as a peg? assumptions?

Answer 18

• a support from which a body can be suspended or rested
• dimensionless and fixed
• can be rough or smooth as specified

Question 19

What does it mean if we refer to air resistance?

Answer 19

• resistance experienced as an object move through the air
• usually modelled as being negligible

Question 20

What does it mean if we refer to gravity?

Answer 20

• force of attraction between all objects
• acceleration due to gravity is denoted by a lines with smaller diagonal lines coming off it

Question 21

Assumptions about gravity:

Answer 21

• assume that all objects with mass are attracted towards the Earth
• Earth’s gravity is uniform and acts vertically downwards
• g = constant and is taken as 9.8, unless otherwise stated in the question