mechanics

Question 1

particle (model)

Answer 1

dimensions of the object are negligible

Question 2

particle (model assumptions)

Answer 2

mass of the object is concentrated at a single point

rotational forces and air resistance can be ignored

Question 3

rod (model)

Answer 3

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

Question 4

rod (model assumptions)

Answer 4

mass is concentrated along a line
no thickness
rigid (does not bend or buckle)

Question 5

lamina (model)

Answer 5

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

Question 6

lamina (model assumptions)

Answer 6

mass is distributed across a flat surface

Question 7

uniform body (model)

Answer 7

mass is distributed evenly

Question 8

uniform body (model assumptions)

Answer 8

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

Question 9

light object (model)

Answer 9

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

Question 10

smooth surface (model assumptions)

Answer 10

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

Question 11

rough surface (model)

Answer 11

if a surface is not smooth its rough

Question 12

wire (model)

Answer 12

rigid thin length of material

Question 13

wire (model assumption)

Answer 13

treated as one-dimensional

Question 14

smooth and light pulley (model)

Answer 14

all pulleys you consider will be smooth and light

Question 15

bead (model)

Answer 15

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

Question 16

bead (model assumption)

Answer 16

moves freely along a wire or string

tension is the same on either side of the bead

Question 17

peg (model)

Answer 17

a support from which a body can be suspended or rested

Question 18

peg (model assumptions)

Answer 18

dimensionless and fixed

can be rough or smooth as specified in question

Question 19

air resistance (model)

Answer 19

resistance experienced as an object moves through the air

Question 20

air resistance (model assumption)

Answer 20

usually modelled as being negilible

Question 21

gravity (model)

Answer 21

force of attraction between all objects. acceleration due to gravity is denoted by g

Question 22

gravity (model assumptions

Answer 22

assume that all objects with mass are attracted towards the earth.
earth’s gravity is uniform and acts vertically.
g is constant and is taken as 9.8ms^-2,unless otherwise stated in the question

Question 23

What is the average velocity formula?

Answer 23

displacement from starting point/time taken

Question 24

What is the average speed formula?

Answer 24

total distance travelled/time taken

Question 25

Define an inextensible string?

Answer 25

a string that does not stretch under load.

Question 26

inextensible string (model assumption)

Answer 26

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

Question 27

light object (model assumption)

Answer 27

treat object as having zero mass

tension is the same at both ends of a light string.

Question 28

What is Newton’s First Law?

Answer 28

An object at rest will stay at rest and that an object moving with constant velocity will continue to move with constant velocity unless an unbalanced force acts on the object.

Question 29

What is Newton’s Second Law?

Answer 29

F = ma

Question 30

What is Newton’s Third Law?

Answer 30

That for every action there’s an equal and opposite reaction.

Question 31

Define resistance?

Answer 31

The force that opposes the motion of a particle

Question 32

Define tension?

Answer 32

a force that prevents two objects moving away from each other.

Question 33

Define thrust?

Answer 33

A force that prevents two objects coming together

Question 34

What are external forces?

Answer 34

Forces produced by something outside the system.

Question 35

Define Friction?

Answer 35

A type of resistance force. It’s always exactly the correct size + direction to keep an object stationary