Section 1: Mechanics

Question 1

What are dimensions

Answer 1

Physical nature of quantity

Each dimension can have many diff units

Question 2

Basic dimensions used in mechanical analysis

Answer 2

Length [L]
Time [T]
Mass [M]

Question 3

SI units

Answer 3

Length: metre (m)
Time: second (s)
Mass: kilogram (kg)

Question 4

Orders of magnitude: 10^x

Answer 4

giga; G; 10^9
mega; M; 10^6
kilo; k; 10^3
centi; c; 10^-2
milli; m; 10^-3
micro; µ; 10^-6
nano; n; 10^-9
pico; p; 10^-12

Question 5

Scalars vs vectors

Answer 5

Scalars are quantities that only have a magnitude (no direction)
Vectors are quantities that have a magnitude and a direction

Question 6

Negative of a vector e.g. -A

Answer 6

In the opposite direction to A

Question 7

Vector multipled by scalar

Answer 7

Gives a vector in the same direction with scalar times the magnitude
If multipled by negative scalar, direction is reversed

Question 8

Uniform motion

Answer 8

Motion in a straight line where the distance covered in any two equal time intervals is the same (i.e. constant speed)

Question 9

Displacement

Answer 9

The distance moved in some direction
Both distance moved and direction are important
Units: m

Question 10

Speed vs velocity

Answer 10

Speed: the distance covered per unit time (irrespective of distance)
Velocity: the displacement per unit time
Instantaneous velocity: the slope of the displacement-time graph at any particular instant
Units: m s^-1

Question 11

Acceleration

Answer 11

Average acceleration: average rate of change of velocity over a time interval
Instantaneous acceleration: the slope of the velocity-time graph at any particular instant
Units: m s^-2

Question 12

Galileo theory

Answer 12

In the absence of any forces, this is the property of a moving object to continue moving in a straight line at constant speed (i.e. constant velocity)

Question 13

Projectile motion

Answer 13

The two components (horizontal and vertical) of the motion of a projectile are independent of one another

Question 14

What is a projectile

Answer 14

Any body projected above the surface of the earth that is unpowered
Only force on the object is gravity once it’s projected

Question 15

What does v(AB) mean

Answer 15

The velocity of observer A with respect to observer B (i.e. the velocity that B sees A moving with)

Question 16

Frame of reference

Answer 16

A coordinate system where the observer is at rest with respect to the coordinate system

Question 17

v(wind)

Answer 17

Air with respect to ground

Question 18

Centripetal acceleration

Answer 18

An object moving at constant speed (v) in a circle has an acceleration towards the centre of the circle

Question 19

Inertial coordinate system / reference frame

Answer 19

Any reference frame that moves with constant velocity, i.e. no acceleration

Question 20

Newton’s 1st law

Answer 20

In the absence of any external forces, when viewed from a reference frame, an object at rest remains at rest, and an object in motion continues in motion with constant velocity
i.e. F = ma

Question 21

Newton’s 2nd law

Answer 21

In an inertial reference frame, the acceleration on an object is equal to the net force on the object divided by the mass
i.e. a = Fnet/m

Question 22

Newton’s 3rd law

Answer 22

If a system A exerts a force on another system B, then B exerts a force of the same magnitude A, but in the opposite direction

i. e. F(A on B) = -F(B on A)
* note: these forces act on diff systems

Question 23

Reaction force AKA…

Answer 23

Normal force

Question 24

Static friction force

Answer 24

No motion (sliding) involved

Question 25

Kinetic friction

Answer 25

Arises when one surface slides along a second surface

Question 26

Isolated system

Answer 26

Doesn’t interact with other systems, so no energy number comes in or goes out of the system

Question 27

Total energy in isolated systems

Answer 27

A number that always remains the same

Question 28

Energy is measured in ____

Answer 28

Joules (J)

Question 29

Kinetic energy number (KE)

Answer 29

The energy number some object has because it’s moving

Question 30

Potential energy number (PE)

Answer 30

The energy number an object has ‘stored’

Can be stored in many diff ways, e.g. gravitational and elastic

Question 31

Total energy number = ?

Answer 31

KE number + PE number

Question 32

Work

Answer 32

The change in the energy of a system resulting from the application of a force acting over a distance

Question 33

Power

Answer 33

The rate at which work is done, i.e. the rate at which energy is transformed from 1 form to another

Question 34

1 W = ?

Answer 34

1 J/s

Question 35

+ve vs -ve values of work

Answer 35

+ve means work is done on the mass, i.e. KE of mass has increased
-ve means energy is being transferred out of mass, i.e. KE of mass has decreased

Question 36

Conservation of momentum

Answer 36

The total momentum of a system remains constant as long as the net external force on the system is zero

Question 37

Momentum - units

Answer 37

kg m/s
Vector quantity (has direction)