Chapter 8: Force and Motion Flashcards
What is force?
A push or pull on an object
How to result in force?
Have interaction with another object.
Can force be seen,can it affect us?
Force cannot be seen, but it can affect us
State 6 types of force.
- gravatitional force
- frictional force
- normal force
- elastic force
- buoyant force
- weight
What is a gravatitional force?
A force that pulls objects toward the centre of Earth
What is a normal force?
A force that acts in perpendicular to the surface of an object
How is normal force produced?
When an object comes in contact with a surface
What is weight?
The weight of an object is defined as the gravatitional force acting on it
What is frictional force?
A force that exists between 2 surfaces that are rubbing each other
What is the relationship between direction of frictional force and direction of object moving?
The direction of the frictional force is opposite to the direction the object moving into
What is elastic force?
A force in an elastic object due to stretching or compression.
Under what condition the object is said to be elastic?
Enable stretched or compressed object to return the object to the original state or length or width
What is a buoyant force?
The thrust force acting on an object that is floating on the surface of a fluid
What are the charateristics of force?
- magnitude
- direction
- point of application
What is magnitude of force?
the amount of force applied
Under vector quantity, what is force’s characteristics?
- magnitude
- direction
What wil happen if a moving object has an external force applied?
it accelerates
How can the magnitude of a force be measured?
using a spring balance
What is the relationship between the weight of object and the length of spring?
When the weight of an object increases, the length of the spring also increases
How to measure weight using the spring balance?
- suspend freely at the hook
- read the reading on the scale that shows the weight of that object
How to measure frictional force using the spring balance?
- pull the object horizontally using the hook until it moves
- read the reading on the scale that shows frictional force
What is the ratio of moon’s gravity and earth’s gravity?
1:4
In what situtation the object doesnt move?
If the net force =0
What is Newton’s third law?
For every action force, there is a reaction force of the same magnitude but in opposite direction
What is the relationship between reaction force and force putten on?
Reaction’s force= force putten on
Does action and reaction force have the same direction and acceleration?
No
What is the effect of force?
- Shape
- Speed
- Position
- Direction
What is the condition for an object to float?
if buoyant force equals to weight of object
What is the formula for buoyant force?
Buoyant force= real weight- apparent weight
What is an apparent weight?
Weight in water
What is the relationship between density and buoyant force?
The stronger the buoyant force the less dense the object
What is the use of a plimsoll line?
Help to determine the safe level for a ship to stay afloat
Why do they need plimsoll lines?
Because all ocean’s density is different
What are levers?
Simple machine to help our work be done easier
Why are levers used?
It uses less force than usual
What are the 3 classes of lever?
First class lever Second class lever Third class lever
What are the 3 positions in levers?
- fulcrum
- load
- effort
What is the effort distance?
Length between effort and fulcrum
What is the load distance?
Length between load and fulcrum
What is the unit of force and load?
Newton, N
Can we use ‘in the centre’ to state things between the lever?
No
What is the first class lever?
fulcrum in between
What is the advantage of a first class lever?
Overcome a large load with small effort
What is the second class lever?
Load in between
What is the relationship between load distance and force used in second class lever?
The shorter the load distance, the less force used
What is the relationship between effort distance and force used in second class lever?
The longer the effort distance, the less force used
What is the advantage of second class lever?
Overcome a large load with small effort
What is third class lever?
Effort in between
What is the relationship between ‘distance between effort and load’ and force used
The longer the distance between effort and load, the more force used
What is the advantage of using a third class lever?
A big effort is necessary to overcome a small load
What is the moment of force?
A force applied to a lever at a distance from the fulcrum
What is the unit and formula for moment of force
Force (N) x Perpendicular distance from fulcrum (m) = Nm (moment of force)
What are the factors affecting the moment of force?
- force
- distance of force from fulcrum
What is the relationship between moment of force and distance of force from fulcrum?
The longer the distance of force from fulcrum, the less force needed
What are the 2 forces that acts in a lever?
- load
- effort
In what condition there will not be a turning effect at the fulcrum?
equal moments of force
What is the formula for equilibrium lever?
L(dl)=E(de)
Load x distane of load from fulcrum= Effort x distance of effort from flcrum
What affects pressure?
surface area
What is the relationship between surface area and pressure exerted?
The larger the surface area, the lower pressure exerted
What is the SI unit and formula for pressure?
Formula: N/m^2
SI unit: pascal (Pa)
What is gas pressure?
The air around us presses on the surfaces of the objects that are in it
What is the kinetic theory of gases?
gases that are tiny, discrete moves constatly and randomly. Therefore, they collide with each other and with walls of containers.
Colliding with a surface exerts a force, causing the air pressure to increases.
What are the factors that affect air pressure?
- volume
- temperature
What is the relationship between volume and air pressure?
The smaller the volume, the higher the air pressure
How to exlain the why when volume is smaller, the air pressure is higher?
Decreasing the volume makes the air particles move about in a smaller space, causing them to collide more often. The force exerted increased, leading to rising of pressure
What is the relationship between temperature and air pressure?
The higher the temperature, the higher the air pressure
How to explain the relationship between temperature and pressure?
When the temperature increases, the air particles recieve more heat energy and move about faster, causing them to collide more often. The force exerted increased, leading to the rise in pressure.
What is atmospheric pressure?
The pressure applied by the atmosphere onto the surface of the Earth and all the bodies on this Earth
State some examples of appliances and devices using atmospheric pressure.
Appliances:
- syringe
- spraying pump
- siphon
- drawing straw
- plunge
- rubber sucker
Devices:
- vacumm cleaner
- bicycle pump
- dropper
- filter pump
- pipette
- bunsen burner
Explain how is atmospheric pressure used in plunger.
The plunger is first pushed downwards to force the air out from under the rubber sucker, creating low air pressure under rubber sucker and high atmospheric pressure outside plunger. The high air pressure in the drainage pipe will push and loosen the blockage, causing the blockage to flow with water
Explain the process of vacummed atmospheric pressure using magdeburg hemisphere
When air is pumped out, the space inside becomes vacuum, making the pressure inside being zero, while atmospheric pressure exerts huge force on hemisphere, making both magdeburg hemispheres difficult to seperate
Explain the usage of atmospheric pressure in drinking straw
When we suck through a drinking straw, the air inside is sucked out, reducing the air pressure inside, leading to high atmospheric pressure that pushes liquid up into the straw
Explain the use of siphon.
transfer liquid from higher level tolower lever
What is altitude?
distance above sea level
State the relationship between altitude and atmospheric pressure.
The higher the altitude, the lower the atmospheric pressure
Why is atmospheric pressure at a lower altitude high?
because most air molecules are pulled by gravatitional force, forcing it to be closer to the ground
Why is atmospheric pressure at a higher altitidue low?
because air molecules are less influenced by gravatitional force, causing them to be lighter and easily expanded
What are the effects of depth on liquid pressure?
Weight of liquid exerting pressure on it.
What is the relationship between depth of liquid and pressure?
The deeper the liquid, the higher the pressure
Why are walls of the dam thicker at the bottom?
Liquid pressure increases with depth and may destroy the wall from bottom if maintained same thickness