forces 2

Question 1

what is work done

Answer 1

when force moves an object through a distance, energy is transferred and work is done

Question 2

what is work done measured in

Answer 2

joules

Question 3

what happens for an object to be in equilibrium

Answer 3

forces are balanced

Question 4

to do you find the value if a missing for of an equilibrium

Answer 4

join given forces tip to toe then measure missing length

Question 5

how do you resolve a force (horizontally and vertically) that is at an awkward angle

Answer 5

measure out the diagonal given then complete the triange in same scale

Question 6

two types of elastic deformation with basic descriptions

Answer 6

elastic deformation:
can return to original shape/length
inelastic deformation:
doesnt return to original shape/length

Question 7

relationship between extension and force

Answer 7

directly proportionate
HOWEVER at “limit of proportionality”, inproportionate

Question 8

what happens to energy when something is elastically deformed

Answer 8

all energy transferred to objects elastic potential energy store

Question 9

apparatus set up to measure link between forces and extension

Answer 9

weighted stand
clamp a spring from top
fixed vertical ruler to measure
hanging mass from bottom of spring

Question 10

pilot experiment for extension practical

Answer 10

• find identical spring to spring used
• add masses one at a time
• measure extension each time
• if there is a bigger increase, limit of proportionality reached and smaller masses are needed

Question 11

method for extension practical

Answer 11

• pilot method first
• measure unweighted length of spring at eye level
• add one mass, allow to rest
• record mass and measure
• record extension (change in length)
• repeat with 5 more masses
• plot force-extension graph

Question 12

how to work out elastic potential energy (work done) of a spring calculated

Answer 12

E = 1/2 k e^2
epe = 1/2 x spring constant (n/m) x extension^2 (m)

Question 13

how can you calculate elastic potential energy store of stretched sprng using graph

Answer 13

area under (linear) graph

Question 14

equation linking weight, mass, gravitational field strength

Answer 14

weight (n) = mass (kg) x gfs (n/kg)

Question 15

equation linking acceleration and change in velocity and time

Answer 15

acceleration (m/s^2) = civ (m/s) / time

Question 16

equation linking final velocity, initial velocity, acceleration, distance

Answer 16

final v^2 - initial v^2 = 2 x acc x dist

Question 17

how is terminal velocity reached in parachutist (sam)

Answer 17

• when sam first falls, gravity much higher than air resistance, accelerate
• as speed increases, so does air res
• eventually they balance, resultant force = 0
• terminal velocity reached
• parachute opens, area for air resistance increases but force pulling down stays the same
• terminal velocity decrease

Question 18

what factors affect terminal velocity

Answer 18

area
shape

Question 19

newtons first law

Answer 19

if resultant force on stationary object is zero it will remain stationary
if resultant force on moving object is zero it will remain moving
ms petosa

Question 20

newtons first law

Answer 20

if resultant force on stationary object is zero it will remain stationary
if resultant force on moving object is zero it will remain moving
ms petosa

Question 21

newtons second law

Answer 21

resultant force = mass x acceleration

Question 22

newtons third law

Answer 22

when two objects interact, forces exerted on each other are equal and opposite

Question 23

set for apparatus to investigate how mass and force affect acceleration practical

Answer 23

• trolley at starting line
• two light gate at stable distances on track, connected to data logger
• pulley attached to trolley
• masses hanging from trolley & pulley

Question 24

what dies trolley/pulley practical investigate

Answer 24

how mass and force affect acceleration

Question 25

what does spring/weights practical investigate

Answer 25

link between forces and extension

Question 26

method for trolley/pulley practial

Answer 26

• connect trolley to string that goes over pulley and connects to masses
• mark starting line for accuracy
• let trolley go without masses to get original acceleration
• repeat, adding one mass, 5 times
• record data from light gates
f

Question 27

equation linking stopping, thinking, and braking distances

Answer 27

stopping d = thinking d + braking d

Question 28

three factors of thinking distance

Answer 28

alcohol
tiredness
distractions

Question 29

4 factors of braking distance

Answer 29

speed
weather/road conditions
tyre conditions
brake conditions

Question 30

equation linking momentum, mass, velocity

Answer 30

momentum (kg m/s) = mass x velocity

Question 31

is momentum vector or scalar

Answer 31

vector

Question 32

relationship between momentum before and momentum after

Answer 32

equal

Question 33

what can conservation of momentum be used for

Answer 33

calculate velocities and masses

Question 34

equation linking force, change in momentum and change in time

Answer 34

force (n) = change in m / change in t

Question 35

why are cars designed to slow people down slowly when they crash

Answer 35

longer it takes for change of m -> smaller change of m -> smaller force -> less casualty

Question 36

three safety car features

Answer 36

crumple zone
seat belt
air bag