Chapter 8 - Modelling in Mechanics

Question 1

What modelling assumption do you make when modelling a particle?

Answer 1

Rotational forces and air resistance can be ignored.

Question 2

What modelling assumption do you make when modelling a rod?

Answer 2

No thickness

Rigid (does not bend or buckle)

Question 3

What model is like a sheet of paper?

Answer 3

Lamina

Question 4

What model has an evenly distributed weight?

Answer 4

A uniform body

Question 5

What modelling assumption do you make when modelling a light object?

Answer 5

That it has zero mass

Tension is the same at both ends of a light string

Question 6

What model does not stretch under load?

Answer 6

Inextensible string

Question 7

What modelling assumption do you make when modelling an inextensible string?

Answer 7

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

Question 8

What modelling assumption do you make when modelling on a smooth surface?

Answer 8

There is no friction

Question 9

What modelling assumption do you make when modelling on a rough surface?

Answer 9

If the objects are moving they experience a frictional force.

Question 10

How do you treat the model of a wire?

Answer 10

One-dimensionally

Question 11

What model is a rigid length of metal?

Answer 11

Wire

Question 12

What modelling assumption do you make when modelling a smooth and light pulley?

Answer 12

That the pulley has no mass

Tension is the same either side of the pulley

Question 13

What models will always be smooth and light?

Answer 13

Pulleys

Question 14

What modelling assumption do you make when modelling a bead?

Answer 14

That is moves freely along a wire or string

Tension is the same either side of the bead

Question 15

What forces act vertically downwards?

Answer 15

Weight and gravitational force

Question 16

What force acts perpendicular to the surface?

Answer 16

Normal reaction

Question 17

What force is friction?

Answer 17

A force which opposes the motion between two rough surfaces

Question 18

What force acts on an object being pulled by a string?

Answer 18

Tension

Question 19

What force does an object experience that is being pushed along using a light rod?

Answer 19

Thrust

Question 20

What is the force which allows a body to float or rise when submerged in a liquid?

Answer 20

Buoyancy

Question 21

What does air resistance do?

Answer 21

Oppose the motion, so acts in the opposite direction of the particle or object.

Question 22

What is the SI unit for mass?

Answer 22

Kg

Question 23

What is the SI unit for length?

Answer 23

m

Question 24

What is the SI unit for time?

Answer 24

s

Question 25

What is the SI unit for speed/velocity?

Answer 25

Metres per second

Question 26

What is the SI unit for acceleration?

Answer 26

Metres per second per second

Question 27

What is the SI unit for weight?

Answer 27

N

Question 28

What is the magnitude of the displacement vector?

Answer 28

Distance

Question 29

What is the magnitude of the velocity vector?

Answer 29

Speed