Topic 1 -forces

Question 1

What is scalar quanitities ?

Answer 1

Scalar quantities have a magnitude (size) only .

-Scalar quanitites do not have a direction .

Question 2

Give a few examples of scalar quantities .

Answer 2

mass , temperature , spepd ,e enrgy , distace , time .

Question 3

What is vector wuantities ?

Answer 3

vector quanitities both have magnitude and direction .

Question 4

GIve a few examples of vector quanitites .

Answer 4

Dispalcement , weight , force , velocity , accleration and momentm

Question 5

Explain dispalcement

Answer 5

Magnitude -(500m as an example )

and direction example (due West )/

Question 6

How can we represnent vectors ?

Answer 6

• Vectors can be reperesetned using an arrow
• Length of the arrow is equal to the magntidue of the vector ,
• Direction of the arrow is direction of the vector .

Question 7

What is the unti for force ?

Answer 7

Newtons .

Question 8

What two quanitites is force dividied into ?

Answer 8

• Contact Froces

- Non contact forces .

Question 9

Examples of contact forces .

Answer 9

Objects thae aare physically touching ,
(tension , friction between two objects causing them to slow down , stop )
air resistance .

Question 10

WHat is normal contct force ?

Answer 10

-Lamp exerts force on tbale , table exeerts force on lamp , only happens if objects are in direct contact .
an object exetrs a force on the surface the surface exerts a force on the object .

Question 11

Examples of noncontact forces .

Answer 11

Objects that are physicaly separated .
Gravaitional forces - atratcts alll objects to other forces .
Electrosatic force - between two chatged objects , same charges repulsion , opposite atraction .
Magnetic force - experinced by objects in a magnetic ofrce .

Question 12

What is a force ?

Answer 12

A force is a push or pull that acts on an object due to its interaction with another object .
-forces are vector qunaities as they have both magnitude and direction .

Question 13

What do Newton’s laws descrie ?

Answer 13

Describe the effect forces have on motion of an object .

Question 14

What is newtons first law ?

Answer 14

• If the resultant force action on a stationary object is zero , objec will remian stationary .
• If resualtant force action on an moving object si zero , it will continue moving in same direction at smae speed (velocity ).

Question 15

If forces are balanced …

Answer 15

Resultant force 0 , object will remian stationary .

Velcoity of an objectc will only change if a resultant ofrce si actiong on an object .

Question 16

If something is moving at a constant sppeeed …

Answer 16

there mus be an eqqual force actiign to on it i opposite direction
Known as resitiive force - friction with air , fricition with road .

Question 17

What is the resulant force ?

Answer 17

-The resulant force is a single force that has the same effect as all the original forces acting otgether , Working out resultant force , we subtract smaller froce from larger force .
to 20right ten to left
-20-10 = 10N to the right

Question 18

How to draw a free body diagram ?
Draw on for 20N to the right
10N -

Answer 18

• Objects are drawn as a point .
• Force are drawn as arrows at the starting point .
• Length of arrow sgiws size of force ,
• direction of arrow direction of force . .

Question 19

meaning of alitituude

Answer 19

height .

Question 20

Draw free body diaram for plane flying at constant velocity nd constant alitutude

Answer 20

• contant alitidue so downwards force weight but also opposite euqal force lift .
• thurst forward porvided by engine . consant velocity , so air resistance acting in opposite direction .

Question 21

As aeroplane is moving at a constant velocity …

Answer 21

Forward and backward forces e baalnce .

Question 22

What if two forces accting at angle ..
Froces acting on object , one magnitude 10n other at 8n with angle 30 degrees beween two forces , calculae resultant forces .

Answer 22

1.dot as object , have a key (like 5 cm is 1n )
- draw 10 n line
use portractor mesaure 30 degrees anfle , then draw 8n line .
-create parallelogram - make 8n line from oroginal 10n line first .
-then 10 n line from 8cm line
-draw line from one side of parallelogram to other side and then thats resultant force .

Question 23

What is gravity ?

Answer 23

A vector quanintit has a magnitude and direction .

Question 24

What is mass ?

Answer 24

Mass tells us how much matter the object has ini it .
Unit of mas is Kg
scalar quanitity as it has no direcgtioin .

Question 25

Key idea about mass .

Answer 25

Mass od an obejct does nt depend where object is (elephan oneaarth 5000 kg , on moon also 5000 kg in space also 5000kg)

Question 26

What is weight ?

Answer 26

- Weight og an object is force acting on it due to gravity . - Unit of weight is newton . - weight of ano onnject odes dpened where it is .

Question 27

What is gravitatoinal field strength of Eafrth ?

Answer 27

9. 8N/kg aka gravitiational field strength - this measures he force of gravity in a particular location . - object on surface of earth , esperiences gravitational force to cenrer of earth .

Question 28

Equation of calculaitng weight ?

Answer 28

Weigt (n)=Mass *Gravitiational field strength (N/kg) | W*mg traingleee .

Question 29

weight of an object ...

Answer 29

is direciotnaly propotional to mass of object . weight fish shape thing to mass . if we double WEIGHT mass also DOUBLES .

Question 30

How d we determine an objects weigth ?

Answer 30

calibrated spring balancce - newton metre . | moon gravitiational field strength 1.6 N/kg

Question 31

What is the ceneter of mass ?

Answer 31

Weight of an object (force due to gravity ) can be considerd to act at a single point - known as centerr of amss .

Question 32

What happens if you push a box ?

Answer 32

-Friction of box causes the temperature to increase . -Chemica energy store in persons muscle is converted to thermal energy store of box . Whenever a force is used to move an object ,, energy is ransferred known as WORK .

Question 33

How do you calculate work done ?

Answer 33

Work done )J) =Force (N)*Distance (m) W*fd traignle -distance must be in line with the force .

Question 34

What happens when a car brakes ?

Answer 34

- Moving an object has a kinetic energys tore - durign braking , brake presses against whell . - Force of fricition now acts beteween brake and the wheel. - Kinetic energy store of car is now moved into thermal energy store of the brakes - Temperature of brakes iscrease athte same ime , car slows down , and it loosees kinetic energy . .

Question 35

Whatd oes it mean distance must be lin line with force .

Answer 35

If a person is walking - weight acts verticlay downwards on vertical ditance , itd the only relevant force , chemical energys tore of human goes to gravititon potential energy .

Question 36

What are elastic materials ?

Answer 36

Materials that will allways return to their original length , or shape if we take away the forces acting on them (rubber band , earser , spring ).Elastic deformation

Question 37

Meanng of elastic deformation ?

Answer 37

Object will return to it s original shape . (strech it ,original shape when force removed compressed , original shape when force removed .)

Question 38

In order to change objects length or shape , need more than one force .

Answer 38

Only oen force acting ons statioonary object , forces no longer balanced , so object will just move not change shape .

Question 39

What are inelastic materials ?

Answer 39

-Do not return to their original shape when forces are removed (polymers ) This inelastic deformtion - it wil remain permanently deformed

Question 40

What is the calculation to strech an elastic object .

Answer 40

Force (N)= Spring constant (n/m( *Extenstion (m) -Sme eqution for compression just e stands for compresion . Joule =N/m

Question 41

When we strech or compress an object ...

Answer 41

we are using a force to do work , Elastic pontential energy stored in an object , work done = elastic potential nergy only true if object NOT INELASTICALLY DEFORMED .

Question 42

Whaat is hookes law ?

Answer 42

The extension of a spring is directly proportional to the force applied , as long as its limit of proportionality not exceeded .

Question 43

Equipment for RQP Hooke's law . indpeendnet -forces s on spring dependent - extenstion of spring -ontrol -set up of equipment ,

Answer 43

``` Clamp stand two boasses calmmps spring with point metre ruler ```

Question 44

1. stage for rqq .

Answer 44

Now place a heavy weight on a clamp stand to stop if from fallig over .

Question 45

2. stage for rqq .

Answer 45

2. next we attach a metre rule and spring . | - Top of spring must be at zero on the metre rule , metre rule ahs to be vertical for accurate readings .

Question 46

3. stage of rqp.

Answer 46

3.Bottom of spring has a wooden splint ttached to it as a poitner , Pointer has to be horizontal or inaccurate readings .

Question 47

4 stage of rqp.

Answer 47

3. Now read posotion of poitner on metre rule . | - this is unstreched length of spring (the length with no force attached )

Question 48

5. stage of rqp.

Answer 48

Hang 1N weight on sprign now read positon of poitner on metre rule . Continue adding as man weight as you need (4 1n weights )

Question 49

6. stage of rqp.

Answer 49

Now work out extension produced by adding each weiight . TO DO THIS SUBRTACT unstreched length from length of each reading .

Question 50

7. stage of rqp.

Answer 50

Plot grpahif extdension (y) against weight (x) . - I rqp meant tow ork out weight of mystery object . - to do this measure extenstion of spring when stone is hanging from it , read from graph to measure wiegt of stone .

Question 51

Facts about the RQP practical .

Answer 51

- Graph is a striaght line goign through the prpigin (zero) . - this itells us extension directly propotioanl to the weight . - Linear (striaght) elationship between force and extension hence striaght line . . - Can see spring is elastic as if we were to remove weight , extension returns to xero .

Question 52

Whathappens if we use a rubber band for rqp ?

Answer 52

Check grpah osn sheet . | -NOn liner relationsji .

Question 53

PROBLEM , what if we add too much weight ?

Answer 53

- Chec what graph looks like striaght and then goes up . - shows non-linear as w hae overstreched spring - the spring would still show an extention even if we tooka ll weight off INELASTIC DEFORMATION ,w e haev exceeded springs limit of proptionality .

Question 54

How do we work out the Spring constant using gtaph ?

Answer 54

-Use striaght bit limit of propotioanlity bit NOT EXCEEDED BIT . Divide force (weight / byt extenstion . Can do for any prt of graph apart from exeeded limit of proportionality .