chapter 8:

Question 1

8.1: what is mechanics?

Answer 1

deals with motion and the action of forces on objects

Question 2

8.2: what is a particle? (modelling assumption)

Answer 2

dimensions of the object are negligible

Question 3

8.2: what is the modelling assumption of particles?

Answer 3

1) mass of object is concentrated at the single point
2) rotational forces and air resistance is ignored

Question 4

8.2: what is a rod? (modelling assumption)

Answer 4

all dimensions but one are negligible, e.g beam or pole

Question 5

8.2: what are the modelling assumption of rods?

Answer 5

1) mass is concentrated on a line
2) no thickness
3) rigid (does not bend or buckle)

Question 6

8.2: what is a lamina? (modelling assumption)

Answer 6

object with an area, but negligible thickness, e.g paper

Question 7

8.2: what are the modelling assumption of lamina?

Answer 7

mass which is distrubuted along a flat surface

Question 8

8.2: what is an uniform body? (modelling assumption)

Answer 8

mass which is distrubuted evenly

Question 9

8.2: what are the modelling assumption of an uniform body?

Answer 9

mass of the object is concentrated at a single point at the centre of the body. CENTRE OF MASS

Question 10

8.2: what is a light object? (modelling assumption)

Answer 10

mass of the object is smaller compared to other masses. e.g, string or pulley

Question 11

8.2: what are the modelling assumptions of a light object?

Answer 11

1) treating the object of having zero mass
2) tension is the same at both ends of the light string

Question 12

8.2: what is an Inextensible string? (modelling assumption)

Answer 12

a string that does not stretch under load

Question 13

8.2: what are the modelling assumptions of an inextensible string?

Answer 13

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

Question 14

8.2: what is a smooth surface? (modelling assumptions)

Answer 14

the surface with no rugosity, so friction is negligible.

Question 15

8.2: what are the modelling assumptions of a smooth surface?

Answer 15

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

Question 16

8.2: what is a rough surface? (modelling assumptions)

Answer 16

if a surface is not smooth, it is rough

Question 17

8.2: what are the modelling assumptions of a rough surface?

Answer 17

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

Question 18

8.2: what is a wire? (modelling assumption)

Answer 18

rigid thin length of wire

Question 19

8.2: what are the modelling assumptions of a length of metal?

Answer 19

treated as a one dimensional

Question 20

8.2: what is a smooth/light pulley? (modelling assumption)

Answer 20

all pulleys you consider will be smooth and light

Question 21

8.2: what are the modelling assumptions of a smooth/light pulley?

Answer 21

1) pulley as no mass
2) tension is the same on either side of the pulley

Question 22

8.2: what is a bead? (modelling assumption)

Answer 22

particle with a hole for threading on a wire or string

Question 23

8.2: what are the modelling assumptions of a bead?

Answer 23

1) moves freely along a wire or string
2) tension is the same on either side of the bead

Question 24

8.2: what is a peg? (modelling assumption)

Answer 24

a support where a body can be suspended or rested

Question 25

8.2: what are the modelling assumptions of a peg?

Answer 25

1) dimensionless and fixed 2) can be rough or smooth

Question 26

8.2: what is air resistance? (modelling assumption)

Answer 26

resistance experienced as an object moves across the air

Question 27

8.2: what are the modelling assumptions of air resistance?

Answer 27

using modelled of negligible

Question 28

8.2: what is gravity? (modelling assumption)

Answer 28

the force of attraction between all objects. gravity = 9.8ms^-2

Question 29

8.2: what are the modelling assumptions of gravity?

Answer 29

1) assuming that all objects with mass are attracted towards the earth. 2) earths gravity is uniform and acts downwards 3) g is constant and is 9.8ms^-2

Question 30

8.3: three types of SI units?

Answer 30

1) mass (kg) 2) length (m) 3) time (sec)

Question 31

8.4: what is a vector?

Answer 31

is a quantity which has both magnitude and direction

Question 32

8.4: name an example of a vector

Answer 32

1) displacement (m) - (distance in a direction) 2) velocity (m s^−1) - rate of change of displacement 3) acceleration (m s^−2) - rate of change of velocity 4) force (N)- described by a magnitude, direction and point of direction

Question 33

8.4: what is a scalar?

Answer 33

only has magnitude

Question 34

8.4: what are some examples of scalars?

Answer 34

1) distance (m) - measure of length 2) speed (m s^−1))- measure how quickly a body moves 3) time (sec) - measure of ongoing events taking place 4) mass (kg)- measure of the quantity of matter contained in an object.

Question 35

8.4: are scalars positive or negative?

Answer 35

positive

Question 36

8.4: are vectors positive or negative?

Answer 36

they can be both