a: space, time, motion

Question 1

position

Answer 1

= placement of an object is given in relation to a reference point

Question 2

displacement

def

Answer 2

= change in position (vector, direction is important)
= final - initial position

Question 3

positive or negative displacement from a graph

Answer 3

graph of a velocity-time graph is above the x-axis ⇒ positive displacement
graph of a velocity-time graph is under the x-axis ⇒ negative displacement

Question 4

distance

Answer 4

length of the path followed (scalar, direction is not important)

Question 5

velocity

def, on a graph

Answer 5

rate of change of position/displacement
gradient of a displacement-time graph

Question 6

average velocity

Answer 6

1. total change in displacement/total time
2. (t): line through starting and endpoint → slope = average velocity
3. v(t): area under v(t)t

Question 7

instantaneous velocity

Answer 7

= velocity at a specific instant
slope of the tangent to the curve at the moment in time

Question 8

speed

def, graph, in relation to velocity

Answer 8

rate of change of distance
gradient of a distance-time graph
magnitude of velocity (speed = |v|)

Question 9

acceleration

def, graph

Answer 9

rate of change of velocity
gradient of a velocity-time graph

Question 10

sign of a ⇒ ?

Answer 10

a > 0 ⇒ positive change in velocity
a < 0 ⇒ negative change in velocity

Question 11

average acceleration

Answer 11

1. total change in velocity / total time
2. v(t): line through starting and endpoint → slope = average acceleration
3. a(t): area under a(t) / t

Question 12

instantaneous acceleration

Answer 12

= acceleration at a specific instant
slope of the tangent to the curve at the moment in time

Question 13

breaking distance

Answer 13

= distance to get from a given velocity to 0 ms

Question 14

uniform motion vs uniform acceleration vs non-uniform acceleration

v, a, v(t)

Answer 14

Uniform motion ⇒ v = const, a = 0 (v(t) is a horizontal line)
Uniform acceleration ⇒ v ≠ const, a = const (v(t) is a straight non-horizontal line)
Non-uniform acceleration ⇒ v ≠ const, a ≠ const (v(t) is a non-straight line)

Question 15

average velocity, displacement for uniform acceleration

Answer 15

average velocity = (u+v)/2
displacement = t(u+v)/2

Question 16

free fall

Answer 16

= motion of a body that experiences only the force of gravity
uniformly accelerated (a = g)

Question 17

projectile motion

Answer 17

• parabolic trajectory (no air resistance)
• happens simultaneously in 2 directions ⇒ vertical (accelerated (free fall or throwing into air, a = ± g)), horizontal (uniform, uX = x/t)

Question 18

projectile motion with air resistance characteristics

Answer 18

• non-parabolic trajectory
• lower maximum height
• shorter range
• lower final velocity
• time going up (max height is reached sooner) < going down (upwards air resistance when going downwards)

Question 19

force

Answer 19

physical quantity describing the interaction between bodies that can change the motion of a body or change its shape or size

Question 20

resultant force

Answer 20

vector sum of all the forces acting on an object
has the same result on the body as all the individual forces acting together on the body

Question 21

field forces

def, examples

Answer 21

act at a distance, without direct contact of two bodies
gravitational force (Fg/W), electric force (Fe), magnetic force (Fm)

Question 22

contact force

Answer 22

forces occurring only in the direct contact of two bodies

Question 23

normal force

Answer 23

reactive force of weight, result of two objects in contact pushing against each other
perpendicular to the surface in contact with the body

Question 24

frictional force

Answer 24

parallel to the plane of contact between the body and the surface impedes motion static vs dynamic friction

Question 25

static friction

Answer 25

between two bodies at rest (Ff ≤ μSFn) | μS ... coeff of stat friction, Fn ... normal force

Question 26

when does an object start to move (friction)

Answer 26

F > μSFn ⇒ object moves in line with the force applied (static friction has been overcome) | μS ... coeff of stat friction, Fn ... normal force

Question 27

dynamic friction

Answer 27

⇒ between two bodies moving relative to each other (Ff = μdFn) | μd ... coeff of dyn friction, Fn ... normal force

Question 28

tension force | appears, magnitude

Answer 28

* experienced by a rope (or wire, etc.) attached to a fixed point when the rope is pulled from the other end or both ends * same magnitude but opposite direction to the applied force

Question 29

elastic restoring force

Answer 29

force that counteracts the force extending or compressing a spring and restores the spring to its natural length

Question 30

natural length

Answer 30

length of the spring when it is not acted upon

Question 31

direction of the elastic restoring force

Answer 31

toward the natural length

Question 32

viscous drag force

Answer 32

force opposing motion when a body moves in a fluid (gas/liquid)

Question 33

buoyancy

Answer 33

* exerted by a fluid on an object partly or wholly immersed in the fluid, that counteracts the weight of the body * caused by the difference in pressure at the top of the body and bottom of it * = weight of fluid displaced * = ρ(fluid)V(object immersed in fluid)g = ρ(fluid)V(fluid displaced)g

Question 34

Newton's first law of motion

Answer 34

body that experiences zero resultant force (equilibrium) will have no acceleration

Question 35

inertia | def

Answer 35

the natural tendency of an object to resist changes in its state of motion, including changes to speed or direction | more mass ⇒ greater resistance to changes in motion ⇒ greater inertia

Question 36

what is equilibrium?

Answer 36

resultant force = 0

Question 37

Newton's second law

Answer 37

acceleration of a body depends on the mass of the body and the resultant force acting on the body

Question 38

Newton's third law

Answer 38

any two bodies interact by applying forces on each other which are equal in magnitude and opposite in direction

Question 39

direction of the vector of momentum

Answer 39

same as the direction of velocity

Question 40

internal force

Answer 40

acts on the system from within the system

Question 41

external force

Answer 41

acts on the system from outside the system (weight)

Question 42

linear momentum and resultant force

Answer 42

momentum remains constant unless the system is acted upon by an external resultant force resultant force = 0 ⇒ Δp = pfinal – pinitial = 0

Question 43

impulse | def, graph

Answer 43

change in momentum of a body ⇒ J = FΔt = Δp area under F(t) | F ... average resultant force

Question 44

collision

Answer 44

= impact between objects in which the bodies interact with each other and exert a force on each other

Question 45

collisions in an isolated system and its impact on momentum

Answer 45

total momentum is always conserved: Σp initial = Σp final

Question 46

elastic vs inelastic collision

Answer 46

**elastic** collision ⇒ total kinetic energy is conserved **inelastic** collision ⇒ total kinetic energy is less than prior to collision

Question 47

explosion

Answer 47

= two (or more) bodies are initially at rest and exert forces on each other, moving apart rapidly inelastic collision inversed (kinetic energy is not conserved, momentum is conserved)

Question 48

period and frequency

Answer 48

Period (T) = time of one revolution [sec] Frequency (f) = revolutions in a second [1/s = Hz]

Question 49

angle travelled from a given point in circular motion

Answer 49

θ = s/r | s ... circular path, r ... radius, θ ... angle

Question 50

linear velocity (speed) in circular motion

Answer 50

rate of change of arc length covered uniform circular motion ⇒ |v| is constant but it is tangent to the circle so direction is always changing

Question 51

angular velocity in circular motion

Answer 51

rate of change of the angle covered ⇒ ω = θ/t [rad/s]

Question 52

centripetal acceleration

Answer 52

acceleration experienced by a body as the body moves in circular motion due to the changing direction of velocity points towards the centre of the circle

Question 53

centripetal force | def, how it is calculated, consequence, provided by

Answer 53

* = resultant force exerted along the radial axis on any object that moves on a circular path * F = maC + forces directed towards the center of the circle * perpendicular to velocity * causes body to change direction and accelerate * always provided by another force (tension, friction, normal) | aC ... centripetal acceleration

Question 54

energy transfer mechanisms

Answer 54

a force of one object acts on another ⇒ work (W [J]) a temperature difference exists ⇒ heat (Q [J])

Question 55

work | def

Answer 55

= amount of energy transferred when an external force moves an object over a displacement W = Fs cosθ

Question 56

what forces do work?

Answer 56

only forces acting parallel to displacement do work

Question 57

relationship between work done by external forces and mechanical energy

Answer 57

work done by all external forces = ΔEK + ΔEgp + ΔEep

Question 58

conservation of energy

Answer 58

⇒ energy cannot be created or destroyed, but only transferred from one store to another ΣE initial = ΣE final

Question 59

power

Answer 59

rate of work done/energy transfer

Question 60

efficiency

Answer 60

ղ = useful E / total input E = useful P / total input P

Question 61

fuel

Answer 61

substance that can be made to react with other substances in order to transfer thermal energy or mechanical energy that can be used to do work

Question 62

energy

Answer 62

amount of energy in a fuel per unit volume [J/m3]

Question 63

what does it mean for a force to do work on an object?

Answer 63

energy is transferred to the object

Question 64

work when F(resultant) ≠ 0

Answer 64

there is a force acting on it (F = ma → there is an acceleration → kinetic energy is changed)

Question 65

work when F(resultant) = 0

Answer 65

no work done ⇒ no change to energy (kinetic energy is constant → no acceleration)

Question 66

Sankey diagrams

Answer 66

shows where input energy goes/what it is converted to * arrow thickness = proportional to amount of energy in each store * down arrow = wasted energy * right arrow = useful * each arrow = different store (name the store, amount of energy)

Question 67

energy density

Answer 67

= amount of energy in a fuel per unit volume [J/m3]