Chap 8

Question 1

what is force

Answer 1

force is a pull or a push upon an object

Question 2

Force may exist in various forms/types such as :

Answer 2

gravitational force
weight
normal force
frictional force
elastic force
buoyant force

Question 3

Explain gravitational force

Answer 3

-the force that points towards the centre of the earth
-causes all object that r thrown upwards to fall back to earth

Question 4

explain normal force

Answer 4

-force produced when an object is in contact w a surface

Question 5

explain weight

Answer 5

• defined as the gravitational force acting on it

Question 6

explain elastic force

Answer 6

• exists when a material is stretched or compressed

Question 7

explain buoyant force

Answer 7

• the thrust force acting on an object that is floating on the surface of a fluid

Question 8

explain frictional force

Answer 8

• the force that resists movement between two surfaces that r in contact w each other
  -acts in the opposite direction of the motion

Question 9

Characteristic of force

Answer 9

• is a vector quantity that has magnitude n direction
  -has point of application
  -magnitude is the quantity or value of a measuremt

Question 10

S.I. unit of force

Answer 10

Newton (N)

Question 11

How do we measure force

Answer 11

• using a spring balance
• spring balance operates based on the principle of spring extension

Question 12

100g has a weight of _____ N
1kg has a weight of ____ N

Answer 12

1 N
10N

Question 13

Newtons third law states:

Answer 13

that for every action force, there is a reaction force of the same magnitude but in the opposite direction

Question 14

Force cannot be seen but

Answer 14

its effects can be felt

Question 15

force can change the:

Answer 15

shape, size and motion of the object

Question 16

state the effects of force

Answer 16

-moving stationary object
- stopping a moving object
- changing the speed of an object that is in motion
-changing the direction of motion of an object
-changing the shape and size of an object

Question 17

Explain buoyant force

Answer 17

-object will only float if the buoyant force acting on it is enough to support its weight
-will submerge if not enough

Question 18

Actual weight means

Answer 18

weight of an object in the air

Question 19

apparent weight means

Answer 19

weight of an object immersed in fluid

Question 20

Explain how does an object float in fluid

Answer 20

-buoyant force pushes the object up to the surface bcuz the object is less dense than the liquid is when in the liquid

Question 21

Why are cargo ships marked with plimsoll lines

Answer 21

• for safety purposes
• density of sea water is diff in diff parts of the world cuz of the temp and concentration in salt
• plimsoll lines will help to determine the safe level for a ship to stay afloat

Question 22

what is a lever

Answer 22

a bar that rotates on a fixed point

Question 23

lever is made up of 3 parts, which are:

Answer 23

• Effort
• Load
• fulcrum

Question 24

Explain the 3 parts of a lever

Answer 24

Effort: force applied on the bar
Load: Object to be moved
Fulcrum: Fixed support point

Question 25

Explain purposes of lever

Answer 25

- allows us to do work easily - allows us to use minimal force to do work

Question 26

levers are classified into 3 types:

Answer 26

-first class -second class -third class

Question 27

When does a lever classify as a first class lever

Answer 27

- fulcrum is between lad and effort

Question 28

when does a lever classify as a second class lever

Answer 28

-load is between fulcrum and effort

Question 29

when does a lever classify as a third class lever

Answer 29

- effort is between fulcrum and load

Question 30

WHat does moment of force mean

Answer 30

- the turning effect produced when a force acting on an object can rotate the object at a fixed point

Question 31

Elaborate more abt moment of force:

Answer 31

- allows us to do work easily - depends on the force applied & the perpendicular distance of the fulcrum to the force

Question 32

Force is always towards:

Answer 32

where we pull

Question 33

Method to calculate force:

Answer 33

Moment of force = Force (N) x perpendicular distance from the pivot to the force (m) Simplified: MOF= (N x M)

Question 34

Unit for moment of force is

Answer 34

newton metre ( N m)

Question 35

moment of force has 2 directions

Answer 35

- either clockwise or anticlockwise

Question 36

moment of force will increase if:

Answer 36

- magnitude of force increases, by applying a greater force - perpendicular distance from pivot to effort increases

Question 37

Greater moment of force is produced when:

Answer 37

force is applied at a greater distance from the turning point

Question 38

Formula to solve daily life problems involving levers

Answer 38

Load (N) x Distance of load from fulcrum (m) = Effort (N) x Distance of effort from fulcrum (m) simplified: N x distance of load (m) = N x distance of effort (m)

Question 39

S.I unit for pressure

Answer 39

pascal (Pa)

Question 40

1 Pa equals

Answer 40

1 newton per square metre ( N m-² )

Question 41

Pressure =

Answer 41

Force (N) / Surface area (m²)

Question 42

The smaller the _______, the _______ it is for that thing to be pressed

Answer 42

-surface area -easier

Question 43

pressure defined as

Answer 43

force per unit area

Question 44

Kinetic theory of gas states:

Answer 44

air molecules always move about freely and collide with the walls of its container

Question 45

Whats air pressure

Answer 45

- the force that pushes against the walls and is produced as a result of the frequency of collision between the air molecules and the walls of the container

Question 46

Factors that affect air pressure

Answer 46

-volume -temp

Question 47

what happens when a close container is compressed

Answer 47

-volume in the container is reduced - causes the air particles to collide more frequently w the walls of the container - air pressure in the container increases

Question 48

What happens when air temp in a closed container increases

Answer 48

- air particles move faster - causes air particles to collide w the walls of container more frequently and w a greater force -air pressure increases

Question 49

the lower the temp, the ____ the movement of air particles

Answer 49

-slower

Question 50

the higher the temp, the ___ the movement of air particles

Answer 50

- faster

Question 51

What causes a packet to compress when drink is sucked out

Answer 51

- the drink inside becomes a partial vacuum -air pressure inside decreases -the higher the air pressure outside will press onto the packet and compress it

Question 52

what is the air pressure outside called

Answer 52

atmospheric pressure ( aka the pressure exerted by the atmosphere on the surface n all objects on earth )

Question 53

examples of application of the concept of air pressure in daily life

Answer 53

-plunger -magdeburg hemisphere -straw -syphon -syringe -vacuum cleaner

Question 54

atmospheric pressure ____ as altitude increases

Answer 54

-decreases

Question 55

Explain gravitational attraction

Answer 55

- air molecules closer to the surface of the earth r pulled tgt by the gravitational attraction causing a rise in pressure - at higher altitudes, air molecules are less affected by the gravitational attraction, so air becomes less heavy n expands easily -causes a low atmospheric pressure at high altitude

Question 56

Liquid pressure decreases as the:

Answer 56

depth of liquid decreases

Question 57

Liquid has more pressure at the _

Answer 57

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