P5 Forces and Density

Question 1

how do you calculate mass?

Answer 1

volume x density
or
weight / gravity

Question 2

how do you measure the volume of an irregular object?

Answer 2

displacement of water

Question 3

how do you calculate density?

Answer 3

mass/volume

Question 4

how do you calculate volume?

Answer 4

mass/density

Question 5

what is the tool used to measure very small distances?

Answer 5

micrometer screw gauge

Question 6

what is force?

Answer 6

a PUSH/PULL that can change the SIZE, SHAPE and MOTION of a body

Question 7

what is force measured in?

Answer 7

Newtons (N)

Question 8

how do we draw force diagrams?

Answer 8

ARROW shows direction

LABEL (…N) shows magnitude

Question 9

what is a resultant force?

Answer 9

the net force acting on an object

Question 10

what happens when forces are balanced?

Answer 10

• no resultant force

- object at rest or constant speed in straight line

Question 11

what happens when forces are unbalanced?

Answer 11

• there’s a resultant force

- the object accelerating or decelerating

Question 12

F = ?

Answer 12

ma (newton’s 2nd law)

kx (hooke’s law)

Question 13

what does F=ma tell us?

Answer 13

• force directly proportional to acceleration

- mass inversely proportional to acceleration

Question 14

what is friction?

Answer 14

force that opposes motion + produces heat

Question 15

what is air resistance?

Answer 15

friction due to movement through air.

Question 16

what is the difference between mass and weight?

Answer 16

M: the amount of matter, kg, doesn’t change
W: force of gravitational field strength on mass, N, changes w gravity

Question 17

how do you calculate weight?

Answer 17

mass x gravity

Question 18

unit for mass

Answer 18

kg

Question 19

how do you calculate gravity?

Answer 19

weight / mass

Question 20

what is hooke’s law?

Answer 20

force is directly proportional to extension (F = kx)

Question 21

what are k and x in F=kx?

Answer 21

k is spring constant

x is extension

Question 22

what is the limit of proportionality?

Answer 22

• the point at which Hooke’s Law no longer applies

- graph no longer linear

Question 23

what happens if we keep adding more load to a spring?

Answer 23

1. reaches limit of proportionality and hooke’s law no longer applies
2. breaks

Question 24

what is the centre of mass?

Answer 24

where the mass of an object is concentrated

Question 25

how do you determine an irregular object’s centre of mass?

Answer 25

1. hang lamina from a point
2. mark vertical line
3. hang lamina from second point
4. mark second vertical line
   → centre of mass is there the lines intersect

Question 26

how does weight act on an object?

Answer 26

from centre of mass

vertically downwards

Question 27

when does an object fall?

Answer 27

when the centre of mass falls beyond either side of the base

Question 28

what is MOMENT?

Answer 28

TURNING EFFECT away from centre of mass

Question 29

when would you say a system is in equilibrium?

Answer 29

no resultant force

no turning effect

Question 30

how do you calculate moment?

Answer 30

distance from pivot x perpendicular force

Question 31

define gravitational field + example

Answer 31

where mass experiences force

e.g. earth

Question 32

what is upthrust?

Answer 32

the upward force that a liquid or gas exerts on a body

Question 33

what does a directly proportional graph look like?

Answer 33

• straight line

- through the origin