forces + work done

Question 1

what is the impact of a tsunami on a coastal region?

Answer 1

→ what? (2 or more)

→ how? (e.g. damage, kill)

A tsunami can cause damage to buildings and the environment near the shoreline, erosion of coastlines and loss of lives

Question 2

what are tsunamis?

Answer 2

vigrous movement of the ocean floor caused by earthquakes or vocalnic eruptions displaces the ocean water and results in tsunamis.

Question 3

explain why the extent of destruction on a coastal region can be very great

Answer 3

• high speed and/or great heights
• impact: high energy, therefore damage

A tsunami is a series of successive ocean waves which travel at high speeds, and can reach great heights especially on low lying areas. the waves that hit the coastal areas have high energies, causing damage to infrasturcture and lives

Question 4

why should people in places that have been hit by a tsunami be aware that danger may not have passed after the first wave of the tsunami?

Answer 4

• what is a tsunami? : a series of successive waves
• what does the series do? : destructive force multipled
  A tsunami is usually composed of a series of successive waves. Its destructive force may be multiplied as sucessive waves reach the coastal area.

Question 5

how does science and technology can be used to monitor or reduce the impact of natural disasters?

Answer 5

1. earthquake-prone countries build earthquake resistant buildings
2. use artificial intelligence to predict earthquakes
3. mobile applications provide disaster alerts
4. use aerial robotics to capture aerial images or video of damages caused by disasters to support rescue or recovery efforts

Question 6

when writing explanation

Answer 6

use claim evidence reasoning

Question 7

when circling example of force, focus on object where it takes place:

Answer 7

• frictional force: surfaces in contact
• gravitational force: object where it takes place
• elastic force: spring

Question 8

turning effect of force

Answer 8

a force can cause an object to rotate about a fixed point

Question 9

how can a screwdriver help remove lid of can

Answer 9

The screwdriver can be used to apply an upward force at the small edge of the tin to remove the lid of the tin can.
This happens when you apply a downward force at the other end of the screwdriver with your hands.
This results in a turning effect about a fixed point at the lid where screwdriver is placed, making the lid easier to remove compared to using your bare fingers.

Question 10

what is friction

Answer 10

Friction opposes the motion between two surfaaces that are in contact with each other

Question 11

factors affecting friction

Answer 11

• Degree of roughness of materialThe rougher the surfaces in contact, The greater the magnitude of friction (leather and rubber generate significant amounts of friction, glass generate relatively small amounts)
• Pressing ForceAmount of friction generated is proportional to the magnitude of the force that presses the two objects together (when object is sliding on floor, pressing force is weight of the block)

Question 12

advantages of friction

Answer 12

1. Friction between the floor and the soles of feeet prevents people from slipping when they walk
2. Friction allows people to grip objects with their hands (ridged skin that forms fingerprints creates greater friction to make gripping easier)
3. Friction between the wheels and ground allows vehicles to move
4. Friction converts kinetic energy to thermal energy

Question 13

disadvantages

Answer 13

1. Friction can be wasteful because it converts the kinetic energy of motion into thermal energy
   
   1. thermal energy can cause wear and tear of surfaces, resulting in costly waste of materials
   2. increase amount of energy machines need to do work, reducing efficiency
2. Friction in the form of air resistance and water resistance decreases speed of moving objects

Question 14

elastic force

Answer 14

elastic force is the force that acts on a stretched or compressed elastic object to return the object to its original shape

Question 15

factors affecting elastic force

Answer 15

• stiff springs (leads to more ef)
• greater extension (more ef)
• number of springs
• arrangement of springs

Question 16

Gravitational force

Answer 16

a force of attraction between objects that have mass

Question 17

mass

Answer 17

• the amount of matter in an object
  -kg
• beam balance/ electronic balance
• constant regardless of location

Question 18

weight

Answer 18

the amountof gravitational force acting on an object
newton
spring balance
may vary depending on location

Question 19

effects of force

Answer 19

• change the shape and size of an object
• the movement of a stationary object
• halt in movement of a moving object
• change in speed of a moving object

Question 20

changes in the state of rest or motion of an object

Answer 20

when a force exerted causes the transfer of energy between objects, the state of rest or motion of the objects may change

Question 21

how does a force cause change in state of rest or motion?

Answer 21

when a force exerted causes the transfer of energy between objects, it can:

• move a stationary object
• change speed
• change direction
• stop a moving object

Question 22

changes in size and/or shape of an object

Answer 22

when a force exerted causes the transfer of energy between objects, the size/shape of the objects may change

Question 23

real life application of changes in shaoe and size

Answer 23

balloon changes in size when air is pumped into it, sponge changes in shape when a force is applied to squeeze it

Question 24

spring balance

Answer 24

he more the spring in the spring balance is extended, the greater the weight (force) applied on it.

Question 25

pressure

Answer 25

the force exerted per unit area, Pa

Question 26

if too much pressure is exerted by a vehicle on its tyres, the tyres might burst. hence, explain why larger vehicles such as lorries have wider tyres and greater number of wheels

Answer 26

- larger vehicles have a greater weight than smaller vehicles, thus exerting a greater downward force on their tyres - having a wider and greater number of tyres increases contact area of the tyres wth the vehicle - since pressure is the force exerted per unit area, - this decreases pressure exerted by heavy vehicle

Question 27

bases of scaffolding are fitted with metal plates. how does it affect pressure exerted by scaffolding on ground?

Answer 27

- the metal plates increases contact area of the scaffolding with the ground - since pressure is the force exerted per unit area - this results in less pressure exerted on the ground due to weight of scaffolding

Question 28

why the shopper’s hnd hurts when he carries the bag

Answer 28

- handles have a small contact area with the shopper’s hand - since pressure is the force exerted per unit area - this results in large pressure exerted by handles on hand, making the shoppers hand hurt

Question 29

camel flat feet why?

Answer 29

a camel has large, flat feet to spread its weight out over a large area, thus pressure exerted by the camel on sandy ground is low, preventing it from sinking into the sand

Question 30

sharp knife better than blunt knife

Answer 30

cutting edge of a sharp knife is extremely narrow to reduce its area of contact with the surface that is being cut, which causes extremely high pressure to be exertedon the surface when a force is applied by the user as compared to the cutting edge of a blunt knife, which has a larger contact area

Question 31

injection needle sharp?

Answer 31

injection needle needs to be very sharp so that area in contract of the needle with skin is very small. when we apply a force on the needle, a high pressure allows the sharp needle to pierce skin easily

Question 32

high heel shoe break phone screen, sneaker never

Answer 32

heel of high-heeled shoe has a smaller area of contact with a surface than the heel of a sneaker. if hh shoe steps on phone, screen will crack due to high pressure exerted. however if sneaker, screen may not crack due to lower pressure exerted on it

Question 33

pressure in fluids relationship

Answer 33

the deeper the object is immersed in the fluid, the greater the pressure exerted by the fluid on the object

Question 34

why submarine need to have strong body

Answer 34

as the underwater depth of a submarine increases, the pressure exerted on the submarine by the water also increases

Question 35

atmospheric pressure

Answer 35

the pressure exerted on the surface of earth by the weight of the air in the atmosphere

Question 36

atmopheric pressure relationship

Answer 36

if an object is higher up in the atmosphere, then the atmospheric pressure acting on the object decreases

Question 37

atmospheric pressure (sea level vs top of mountain)

Answer 37

higher atmospheric pressure exprienced at sea level compared to lower atmospheric pressure experienced on top of mountain

Question 38

fluid flowing

Answer 38

fluid always flow from a region of higher pressure to a region of lower pressure

Question 39

drinking straw

Answer 39

when drinking through a straw, sucking out the air from inside the straw reduces the air pressure inside the straw, making it lower than the surrounding air pressure, which causes the higher surrounding air pressure to push the water into the straw

Question 40

suction cup

Answer 40

1. when we press a suction cup hook against a smooth surface like a wall tile, air is pushed out from under the suction cup 2. the air pressure between suction cup and the surfaces decreases 3. becomes lower than surface pressure 4. higher atmospheric pressure pushes the suction cup hook towards the smooth surface and holds it in place

Question 41

dam

Answer 41

1. the base of the dam has a much thicker wall than its top 2. water pressure is higher at the base of the dam and a thicker wall is better able to withstand the higher pressure

Question 42

submarine

Answer 42

1. submarines dives to great depths underwater and the internal pressure must be maintained at constant atmospheric pressure but 2. the pressure deep below the water surface can be very high 3. submarine needs a strong body to withstand this pressure

Question 43

work done

Answer 43

work is done when an applied force on a body results in a motion of the body in the direction of the force, and energy is transferred

Question 44

tropical cyclones

Answer 44

tropical cyclones are longer and more intense storms that begin over warm oceans in tropical regions - usually accompanied by heavy rain and strong winds - heavy rain: causes flooding - rapidly moving floodwaters can exert forces on the soil and loosen it, resulting in landslides

Question 45

impacts of tropical cyclones

Answer 45

flooding due to heavy rain →landslides due to rapidly moving floodwaters that exert great forces on the soil and loosen it → strong winds can exert great forces on objects that are in their way, such as vehicles, buildings, trees and even people. broken parts of objects that are carried away by the strong winds can cause damage to surrounding objects, or hit people that injure them

Question 46

earthquakes

Answer 46

the surface of earth is made up of huge pieces of solid rock called plates. These plates countinuously move around very slowly. When a plate slides over or against another plate, the force exerted between the two plates may result in a great amount of energy released. which is exerpienced as earthquakes

Question 47

volcanic eruption

Answer 47

1. deep inside earth, rocks melt to form magma 2. earth moves violently when magma is pushed out towards earth surface with great force 3. results in volcanic eruption 4. a great amount of energy stored within earth is released as heat, light and kinetic energy of the magma impact: volcanic eruption an cuase serious damage to nearby towns and villages

Question 48

factors affecting elastic force

Answer 48

Factors affecting elastic force - stiff springs (leads to more ef) - greater extension (more ef) - number of springs - arrangement of springs

Question 49

Explain how tsunamis generate powerful impacts when they reach coastal areas.

Answer 49

vigrous movement of the ocean floor caused by earthquakes or vocalnic eruptions displaces the ocean water and results in tsunamis. these huge waves can reach great heights. 3. increases gravitational potential energy of ocen water 4. when waves fall from such heights, the gravitational potential energy in waves is converted to kinetic energy as they approach the shore 5. the waves move at high speed and strike objects along the shore with great force

Question 50

contact forces

Answer 50

the force is exerted on objects which are in physical contact with each other, the force applied is called contact force.

Question 51

non-contact

Answer 51

A non-contact force is a force applied to an object by another body that is not in direct contact with it.