Forces - elasticity, pressure, moments

Question 1

Hookes law equation

Answer 1

force = spring constant x extension

Question 2

what is deformation

Answer 2

a change in shape

Question 3

what is elastic deformation

Answer 3

where the deformation is reversed when the force is removed

Question 4

what is inelastic deformation

Answer 4

where the deformation is not fully reversed when the force is removed - there is a permanent change in shape

Question 5

examples of elastic and inelastic deformation

Answer 5

elastic - rubber band
inelastic - metal can being squashed

Question 6

in order to change the length or shape of an object, what has to be done

Answer 6

more than one force has to be applied on it

Question 7

what would happen if we only applied one force on a stationary object

Answer 7

the forces would no longer be balanced, so the object would just move rather than change shape

Question 8

what is stored in elastic objects

Answer 8

elastic potential energy

Question 9

describe how to investigate the relationship between the force and extension for a spring (equipment)

Answer 9

• a clamp stand
• 2 clamp bosses
• two clamps
• heavy weight
• metre rule
• spring
• pointer (wooden splint)

Question 10

why should the pointer be horizontal

Answer 10

because if its not, readings would be inncaurate

Question 11

describe how to investigate the relationship between the force and extension for a spring practical

Answer 11

1. Set up a clamp stand with 2 clamp bosses and 2 clamps
2. Place a heavy weight on the clamp stand
3. Attach a metre rule and a spring to the stand
4. Allign the top of the spring to zero on the metre rule
5. Read the position of the pointer (wooden splint on the bottom of the spring) on the metre rule
   - this is the unstretched length of the spring
6. hang a 1N weight on the spring
7. read the position of the pointer on the metre rule
8. Keep adding 1 N weights every time and reading the pointer position
9. To work out the extension produced, subtract the length of the unstretched spring from each reading
10. Plot the extension against the weight
11. identify the the range of force over which the extension of the spring is directly proportional to the weight hanging from it

Question 12

why do we place a heavy weight on the stand

Answer 12

to stop it from falling over

Question 13

control variables of elasticity practical

Answer 13

• placement of ruler
• placement of spring

Question 14

what should the results be from the elasticity experiment

Answer 14

extension is directly proportional to the weight
- straight line going through the origin
- linear relationship- straight line

Question 15

what happens if you add too much weight to the springs

Answer 15

even after the weights are removed, the spring will still have some extension, so it’ll be inelastically deformed

Question 16

how can you find the spring constant using a graph

Answer 16

dividing the force (weight) by the extension

Question 17

when will the spring constant not be the same on a point on graph

Answer 17

if we exceed the limit of proportionality

Question 18

when does extension happen

Answer 18

when an object increases in length

Question 19

what are compressions

Answer 19

regions of high pressure due to particles being close together, happens when an object decreases in length

Question 20

what is spring constant a measure of

Answer 20

the stiffness of a spring up to its limit of proportionality or elastic limit

Question 21

what is limit of proportionality

Answer 21

the point beyond which Hooke’s law is no longer true when stretching a material

Question 22

what is an elastic limit

Answer 22

the furthest point it can be stretched or deformed while being able to return to its previous shape.

Question 23

what does a higher spring constant result in

Answer 23

a stiffer spring

Question 24

what causes an object to rotate

Answer 24

a force or a system of forces

Question 25

what is a moment

Answer 25

the turning effect of a force

Question 26

how to calculate the moment of a force (newton metres)

Answer 26

moment = force x distance

Question 27

what is the rule for distance when calculating a moment

Answer 27

the distance has to be perpendicular from the lines of action of the force to the pivot

Question 28

what do we know about the moment of an object if it is balanced

Answer 28

the anticlockwise and clockwise moment are equal
the force x distance in the clockwise direction = the force x distance in the anticlockwise direction

Question 29

how can we explain (using moments) why an object can topple

Answer 29

• if you tilt an object, there comes a point where the line of action of the weight lies just outside the base of the object
• now, there’ll be a resultant (unbalanced) moment acting on the block
• this’ll cause the block to topple

Question 30

what are levers

Answer 30

force multipliers that allow us to lift heavy objects by applying a relatively small amount of force

Question 31

what do gears and levers do

Answer 31

transmit the turning effect of a force

Question 32

what does the turning effect in gears depend on

Answer 32

the distance between the edge of the gear and the centre

Question 33

how often does the smaller gear turn compared to the bigger one

Answer 33

2:1

Question 34

what are elastic materials

Answer 34

materials which will always return to their original length or shape if we take away the forces acting on them

Question 35

force equation using spring constant

Answer 35

F =ke

Question 36

what type of energy is stored in an elastic material

Answer 36

elastic potential energy

Question 37

elastic potential energy is equal tooo….

Answer 37

work done

Question 38

why should the metre rule be vertical

Answer 38

so we get accurate readings

Question 39

what is the unit for moment

Answer 39

Nm

Question 40

examples of things you find gears in

Answer 40

cars