Forces and motion

Question 1

State the unit for speed/velocity

Answer 1

m/s

Question 2

State the difference between speed and velocity

Answer 2

direction is specified when talking about velocity

Question 3

speed =

Answer 3

distance/time

Question 4

acceleration =

Answer 4

change in velocity/time

Question 5

What is an orbit ?

Answer 5

balance between the forward motion of the object and the force of gravity pulling it inwards

Question 6

what is mass ?

Answer 6

amount of matter in an object

stays the same where ever you are

Question 7

what is weight ?

Answer 7

the force of gravity on the object

changes on different planets

Question 8

what is the unit for mass?

what is it measured by?

Answer 8

kg

measured using scales

Question 9

what is the unit for weight ?

what is it measured by?

Answer 9

n

measured using a spring balance or newton meter

Question 10

weight =

Answer 10

mass x gravitational field strength

Question 11

state the gravitational field strength on earth/moon

Answer 11

earth = 10 n/kg
moon = 1.6 n/kg

Question 12

state the straight downwards forces

Answer 12

gravity / weight

Question 13

state the forwards forces

Answer 13

thrust / push / pull

Question 14

state the slowing forces

Answer 14

drag / air resistance / friction

Question 15

State the 3 ways of friction occurring

Answer 15

1. between solid surfaces gripping
2. between solid surfaces sliding
3. air resistance / drag from a fluid

Question 16

what is a fluid ?

Answer 16

liquid or gas

Question 17

Define terminal velocity

Answer 17

the velocity when resistance force becomes equal to accelerating force in free fall (maximum velocity)

Question 18

In free fall, what does the resistance equal?

Answer 18

resistance = weight

Question 19

what are the factors of terminal velocity?

Answer 19

shape and surface area

more surface area = more air resistance

Question 20

State the First Law of Motion

Answer 20

Balanced forces means no change in velocity
no deceleration or acceleration
to keep steady speed there must be 0 resultant force

Question 21

State the Second Law of Motion

Answer 21

Unbalanced force means object will accelerate that direction

resultant forces means acceleration / decceleration

Question 22

What is an unbalanced force called ?

Answer 22

Resultant force

Question 23

Resultant force =

N

Answer 23

mass x acceleration

F = ma

Question 24

State the Third Law of Motion

Answer 24

exerting a force onto and object, exerts the exact force onto you from the object
smaller mass will be affected more by force

Question 25

What are the vector quantities and examples ?

Answer 25

Size and direction | force, velocity, displacement, acceleration, momentum..

Question 26

What are the scalar quantities and examples?

Answer 26

Only size | mass, temp, time, length...

Question 27

What is Stopping distance ?

Answer 27

distance covered from driver spotting hazard to car coming to a complete stop

Question 28

Stopping distance =

Answer 28

Thinking distance + Braking distance

Question 29

What is Thinking distance ?

Answer 29

distance car travels from driver noticing hazard to applying brakes

Question 30

State the factors of thinking diatance

Answer 30

``` speed of car reaction time (drugs/alcohol, tiredness, old age) ```

Question 31

What is Braking distance ?

Answer 31

distance car travels during deceleration until complete stop with brakes being applied

Question 32

State the factors of braking distance

Answer 32

speed of car mass of vehicle condition of brakes grip (road, tyres, weather conditions)

Question 33

momentum =

Answer 33

mass x velocity

Question 34

what is the unit for momentum ?

Answer 34

kg m/s

Question 35

momentum before =

Answer 35

momentum after

Question 36

what causes change in momentum ?

Answer 36

force(s)

Question 37

Force (acting) =

Answer 37

change in momentum / time

Question 38

Describe how crumple zones help

Answer 38

crumple on impact | increase time taken for car to stop

Question 39

Describe how seat belts help

Answer 39

stretch slightly, increasing time taken for wearer to stop | reduces force acting on chest

Question 40

Describe how air bags help

Answer 40

slow you down more gradually | increase time taken for force to reach you

Question 41

why increase time taken for force to reach you (like in a crash)?

Answer 41

faster the momentum changes, larger the forces act on you and more likely to injure you longer it takes for change in momentum, smaller the forces are

Question 42

what is a moment ?

Answer 42

the turning effect of a force

Question 43

State the unit for a moment

Answer 43

Nm

Question 44

Moment =

Answer 44

force x perpendicular distance between line of action and pivot

Question 45

state the principal of moments

Answer 45

Total anticlockwise moments = Total clockwise moments

Question 46

Your younger brother weighs 300 N and sits 2m from pivot. You weigh 700 N, where should you sit?

Answer 46

anticlockwise moment = clockwise moment 300 x 2 = 700 x y y = 0.86m

Question 47

What happens if the anticlockwise moments don't equal clockwise moments ?

Answer 47

there will be a resultant moment | object will turn

Question 48

what is the natural length (l) ?

Answer 48

length of an unstreched metal wire

Question 49

What is a galaxy ?

Answer 49

large collection of stars

Question 50

What are comets ?

Answer 50

small lumps of icy rock which orbit the Sun

Question 51

What happens to an orbit as gravity increases ?

Answer 51

The speed of the orbit increases

Question 52

What is the orbit shape of moons and planets ?

Answer 52

slightly elliptical

Question 53

Describe the orbit of comets

Answer 53

very elliptical and with the Sun at one end | travel much faster near the Sun as increased gravity speeds it up

Question 54

What artificial satellites have an orbital period of 1 day?

Answer 54

geostationary satellites | useful for communications

Question 55

Orbital speed =

Answer 55

(2 x π x orbital radius) / time

Question 56

what is Hooke's law ?

Answer 56

extension of a stretched wire (or spring) is proportional to the load/force

Question 57

what is the elastic limit ?

Answer 57

point where if you increase the force more the material will be permanently stretched and longer than its natural length