topic 8 + 9- forces and energy + density

Question 1

system

Answer 1

a single object or group of objects that you are interested in

Question 2

if a system changes what happene=s

Answer 2

energy is transferred, this can be into or away from the system (between objects ; between energy stores)

Question 3

energy

Answer 3

the capacity of something to do work

Question 4

what does the law of conservation of energy mean for a close system

Answer 4

the total amount of energy in a closed systems remains the same

Question 5

kinetic energy store

Answer 5

energy of a moving object

Question 6

elastic (potential) energy store

Answer 6

energy of a stretched spring or elastic band

Question 7

gravitational (potential) energy store

Answer 7

the energy something gains as it is lifted up

Question 8

electrostatic energy store

Answer 8

energy due to force of attraction between two electrostatic charges

Question 9

magnetic energy store

Answer 9

energy due to the force of attraction between two magnets

Question 10

chemical energy store

Answer 10

energy within a chemical substance

Question 11

thermal energy store

Answer 11

energy of an object due to its temperature

Question 12

nuclear energy store

Answer 12

energy contained within an atom’s nucleus

Question 13

basic energy diagram

Answer 13

initial energy store –> final energy store

Question 14

efficiency

Answer 14

total energy input

Question 15

what is a mechanical transfer

Answer 15

when a force acts on a body, energy can be transferred

Question 16

what is an electrical transfer

Answer 16

electricity can transfer energy from a power source and deliver it to different components of a circuit

Question 17

what is transfer by heating

Answer 17

thermal energy is transferred from place to place by conduction, convection and thermal radiation

Question 18

in all system changes what happens

Answer 18

energy is dissipated to be stored in less useful ways

Question 19

when a force does work to move an object, how is energy transferred

Answer 19

mechanically

Question 20

what is energy transferred/ work done measure in

Answer 20

Joules (J)

Question 21

work done (formula)

Answer 21

work done = force x distance moved

Question 22

change in gravitational potential energy (formula)

Answer 22

change in GPE = mass x GFS x change in height

Question 23

kinetic energy (formula)

Answer 23

kinetic energy = 1/2 x mass x velocity^2

Question 24

what happens if a mechanical process becomes wasteful

Answer 24

there is a rise in temperature due to dissipation of energy heating surroundings

Question 25

power (definition)

Answer 25

the rate of energy transfer

Question 26

power (formula)

Answer 26

power = work done --------------- time taken

Question 27

what is power measured in

Answer 27

watts

Question 28

1 W =

Answer 28

1 J/s

Question 29

force

Answer 29

a push or pull on an object that is caused by it interacting with something

Question 30

normal contact force and friction

Answer 30

acts between all touching objects

Question 31

interaction pair

Answer 31

when two objects interact, both feel an equal but opposite force this pair of forces is an interaction pair

Question 32

give 3 examples of non contact forces

Answer 32

magnetism electrostatism gravity

Question 33

how can an interaction pair be represented

Answer 33

as vectors

Question 34

density

Answer 34

the mass per unit volume of a substance

Question 35

what is density measured in

Answer 35

g/cm^3 OR kg/m^3

Question 36

1g/cm^3 =

Answer 36

1000kg/m^3

Question 37

conditions to float

Answer 37

if a solid has a lower average density than a fluid, then it will float

Question 38

how do you find the density of a fluid

Answer 38

place a measuring cylinder on a balance and zero it pour 10ml of a the liquid in and record its mass pour another 10ml in and record total volume and mass repeat until cylinder is full for each measurement use the formula to find the density take an average

Question 39

how do you find the density of a solid object

Answer 39

use a balance to measure the mass of an object find volume of object - this can be done for some shapes using a regular formula - for other objects in find volume by submerging it in a eureka can ; the water displaced will be transferred to the measuring cylinder record the volume of water in the measuring cylinder use the formula to work out the object's density