3.2.2.3 Linear motion

Question 1

vector quantity

Answer 1

both magnitude and direction

e.g.s displacement, velocity, force, weight, momentum, angular displacement, angular velocity

Question 2

scalar quantity

Answer 2

magnitude only

e.g.s distance, speed, mass, angular distance, angular speed, temperature

Question 3

distance vs displacement

Answer 3

distance: length of path taken from 1 position to another (m)
displacement: shortest route in straight line route between 2 positions (m) (velocity x time)

Question 4

speed vs velocity

Answer 4

speed: rate of change of body’s movement per unit of time (m/s) = distance divided by time
velocity: rate of change of displacement (m/s) = displacement divided by time

Question 5

linear motion

Answer 5

motion in straight or curved line
parts moving same distance at same speed in same direction

centre of gravity along a straight/curved movements = in the same direction

Question 6

vector diagrams

Answer 6

represent movement

• point of application
• line of application
• direction

length of arrow = magnitude

Question 7

e.g. tennis ready position

Answer 7

no movement
weight force & ground reaction force

zero net force = state of inertia (N1)
GRF = W

Question 8

vertical forces

Answer 8

1. weight

2. reaction force (when 2 bodies in contact)

Question 9

e.g jumping up

Answer 9

weight force and GRF 
direction of movement (DOM) upwards 
net force up, upwards acceleration
GRF> W 
N2 
more force = more acceleration 
F=ma (m - constant)

Question 10

horizontal forces

Answer 10

1. friction

2. air resistance

Question 11

e.g. 200m sprinter

Answer 11

accelerating direction of movement to right
point of origin for air resistance is at COM
friction (anti slipping force)
F>AR
net forward force
acceleration

Question 12

e.g. cycling

Answer 12

F=AR 
zero net force 
constant velocity 
(no vertical movement) GRF = W

Question 13

e.g. runner

Answer 13

AR >F
net backwards force
deceleration

Question 14

external force

Answer 14

comes from outside the body

e.g. friction, air resistance, weight, gravity

Question 15

internal force

Answer 15

inside the human body e.g. contraction of muscles
generated by skeletal muscle

internal muscular force: from quadriceps as concentrically contract

Question 16

frictional force

Answer 16

stops athlete slipping
e.g. sprint = max friction to stop slipping

static: no motion between surfaces
sliding: moving relative to one another

affected by:

1. surface characteristics of 2 bodies in contact
2. temperature of 2 surfaces
3. mass of sliding objects

Question 16

air resistance and what its affected by?

Answer 16

opposes motion through air

affected by:

1. velocity of moving body
2. cross sectional area of moving body
3. shape/surface characteristics of moving object

Question 17

impulse

Answer 17

time it takes a force to be applied to an object or body
relevant when 2 objects collide= impact
greater impulse = greater change in momentum

Question 18

impulse is a product of

Answer 18

size of force acting
time the force is applied for
I = Ft

Question 19

force time graph

Answer 19

impulse = area under force time graph
above the line = positive impulse
below the line = negative impulse

Question 20

how does increasing impulses help?

Answer 20

momentum = velocity (outgoing) = acceleration

gradually decrease incoming momentum
e.g. cushioning a catch/crash matt

Question 21

net impulse

Answer 21

combination of positive and negative impulses

Question 22

mass vs weight

Answer 22

mass: quantity of matter the body possesses
weight: gravitational force exerted on an object
gravitational pull of athlete to the ground (increase mass = increase gravitational pull)
(mass x gravity = weight) (kg x 9.8 = N)

Question 23

distance time graph

Answer 23

straight = stationary
increasing straight = constant speed
curved increase = accelerating
curved decrease = deceleration

Question 24

velocity and speed time graphs

Answer 24

straight = constant velocity
curved increase = increase velocity or accelerating
curved decrease = decrease velocity or decelerating
above and below line = above increase is accelerating above decrease is decelerating below line = change of direction

Question 25

deceleration/acceleration

Answer 25

+ve acceleration
-ve deceleration
rate of change of velocity (m/s squared)
change in velocity divided by time

Question 26

change in velocity equation

Answer 26

final velocity - initial velocity divided by time

Question 27

momentum (kg m/s)

Answer 27

amount of motion of an object resulting from mass and velocity

mass (kg) x velocity (m/s)

larger mass and if travel at same velocity = greater momentum

Question 28

in order for linear motion to occur…

Answer 28

force applied directly through COM

occurs alongside angular motion

Question 29

force

Answer 29

push or pull that acts on a body to cause a change in its state of motion (newtons)

Question 30

effect of a force

Answer 30

1. rest to move
2. moving body = change direction accelerate, decelerate
3. change shape of an object (e.g. dive)

Question 31

vertical force vs horizontal force

Answer 31

horizontal > vertical = horizontal trajectory e.g. sprinter

vertical > horizontal = vertical trajectory e.g. high jump

Question 32

free body diagrams/vector diagrams

Answer 32

forces applied to object (body) = arrows
arrow must start at point of application of force
direction of arrow = indicate direction force applied
length line = magnitude of force