linear motion

Question 1

what is linear motion

Answer 1

motion in a straight or curved line
all body parts moving at the same speed in the same direction

Question 2

what is a scalar quantity

Answer 2

has only magnitude (size)
- speed
- mass
- distance

Question 3

what is a vector quantity

Answer 3

has both magnitude and direction
- displacement
- velocity
- acceleration
- momentum
- weight

represented by arrows
length of arrow shows magnitude
longer the arrow, bigger the size
direction shown by line of application

Question 4

what is mass

Answer 4

physical quantity of matter/substance in a body
made of bone, muscle, tissue and fluid
measured in kg
scalar

Question 5

what is weight

Answer 5

force on a given mass due to gravity
measured in newtons
mass x gravity= weight
gravity on earth is 10 n
vector

Question 6

what is distance

Answer 6

measured in metres
path a body takes as it moves from the starting to finishing position

Question 7

what is displacement

Answer 7

measured in metres
shortest route in a straight line between a start and a finsih position

Question 8

what is speed

Answer 8

scalar
rate of change of a position
speed (m/s)= distance (m) / time (s)

Question 9

what is velocity

Answer 9

vector
how fast a body travels in a certain direction
rate of change of displacement
velocity = displacement/time

Question 10

distance time graphs

Answer 10

• line does not go up or down
• no distance travelled. performer is stationary
• constant iagonal direction
• distance run is changing at a constant rate and at the same speed
• curve gets gradually steeper
• more distance covered in a certain amount of time
• performer accelerating
• curve levels off
• less distance covered in a certain amount of time
• performer decelerating

Question 11

velocity time graphs

Answer 11

• gradient remains constant, indicates performer is travelling at a constant velocity
• gradient gets steeper
• indicates the performer is moving with increasing velocity
• gradient decreases
• performer has decreasing velocity (deceleration)
• as curve goes below the x-axis, this means there has been a change in direction

Question 12

what is acceleration

Answer 12

• rate of change of velocity
• when velocity increases, positive acceleration occurs
• when velocity decreases, negative acceleration occurs
• acceleration measured in ms^2

acceleration = change in velocity / time

change in velocity = final velocity - initial velocity

Question 13

what is momentum

Answer 13

• a product of mass and velocity of an object

momentum (kgm/s) = mass x velocity
- vector

Question 14

what is conservation of momentum

Answer 14

when performer or object is in flight
when in flight neither mass or velocity can be altered
mass is constant (unchanged)
velocity can only be altered by external forces

Question 15

what is an internal force

Answer 15

generated by the skeletal muscle

Question 16

what is an external force

Answer 16

comes from outside the body

Question 17

what are vertical forces

Answer 17

gravity/weight, reaction
weight= gravitational force the earth exerts on our body, pulling us down; greater the mass, greater the weight force pulling down
reaction force= for every action there will be an equal and opposite reaction; always a reaction force when 2 bodies are in contact with eachother

Question 18

what are horizontal forces

Answer 18

friction and air resistance
static friction= force exerted when there is no motion between 2 surfaces
sliding friction= when 2 bodies in contact have a tendancy to slip and slide over eachother

Question 19

what is friction affected by

Answer 19

• roughness of the surface
• mass of an object
• temperature of the 2 surfaces- increase in temp reduces friction

Question 20

what is air resistance dependent on

Answer 20

• velocity of the moving body
• frontal cross sectional area of the moving body
• shape and surface characteristics of the moving body

Question 21

free body diagrams

Answer 21

• use arrows
• position, direction and length are important
• weight= force drawn down from centre of mass
• reaction= force that starts from when 2 bodies are in contact
• friction= force starts from 2 bodies are in contact and is opposite to the direction of potential slipping
• air resistance= force drawn from the centre of mass opposing the direction of motion of the body

Question 22

what is a net force

Answer 22

balanced/unbalanced forces
balanced= when 2 or more forces acting on a body equal but opposite
if friction is equal to air resistance, net force is 0
if frictin is greater than AR, acceleration
if frction is less than AR, deceleration

Question 23

what is impulse

Answer 23

time taken for force to be applied
impulse = force x time
impulse is measured as n.s
if impulse increases so does the rate of change in momentum causing a larger change in velocity

Question 24

impulse to increase speed

Answer 24

• increase amount of internal muscular force applied
• increase the amount of time in which the force is applied

Question 25

impulse to decrease speed

Answer 25

• ## increase the time that a force acts on the body/object

Question 26

force time graphs at start of a race

Answer 26

• positive imoulse bigger than negative = acceleration

Question 27

force time graphs in teh middle of a race

Answer 27

• positive and negative impulses are equal
• the net impulse is 0
• there is no acceleration or deceleration
• performer is running at constant velocity

Question 28

force time graphs at the end of a race

Answer 28

• negative impulse is bigger than the positive impulse = deceleration