Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chapter 9 Application of Forces and Transfer of Energy - Coggle Diagram
Chapter 9 Application of Forces and Transfer of Energy
Types of Forces
Definition of Force : A force is a 'push' or 'pull'
SI Unit for force is
Newton (N)
A force can be measured using a force meter
Forces can be classified under 2 types
Contact
forces
Friction
force is the contact force that opposes motion between two surfaces in contact
Elastic
force is the contact force acting on a stretched or compressed elastic object to return to its original shape
Non-Contact
forces
Gravitational
force is the force that attracts two objects towards each other.
Ocean tides are caused partly by the moon's gravity pulling on the waters of the ocean
Gravitational force pulls objects to the ground and prevents them from floating away
Magnetic
force is the force exerted by a magnet and another magnetic materials such as iron, steel, nickel, cobalt
Every magnet has a north pole and a south pole
Unlike poles attract and like poles repel
Comparing Weight and Mass
The
weight
of an object is the gravitational force or force of gravity acting on it
SI Unit of weight is
Newton (N)
Instruments for measuring weight : spring balance(extension/compression)
The gravitational force (weight) is different on different planets
Weight (W) is related to mass (m) and the gravitational field strength (g) of the location
Weight = Mass X Gravitational Field Strength
Decreases when object is moved from the Earth to the Moon
The
mass
of an object is the amount of matter in an object
SI Unit of mass is
Kilogram (kg)
Instruments for measuring mass : electronic balance/beam balance
Remains unchanged (constant) when the object is moved from the Earth to the Moon
Conversion
1kg = 10N
What happens when two or more objects interact
Changes in the state of rest or
motion of an object
A force can
move a stationary object
A force can
change the speed of an object
A force can
change the direction in which an
object moves
A force can
stop a moving object
Changes due to the turning effect of
a force on an object
A force applied on an object can cause a turning effect about a fixed point called the
pivot
Examples : Using a crowbar, Using a wheelbarrow, Using a fishing rod
Changes in size and/or shape of an
object
eg. kneading a piece of plasticine
Changes in pressure on an object
Pressure is an effect of force acting on an object
When the force acting on a surface decreases, the pressure decreases.
When the contact area of the surface
increases, the pressure decreases.
Pressure
Pressure
is the
amount of force applied on a surface per unit area
When the force acting on a
surface decreases
, the
pressure decreases
.
When the
contact area of the surface
increases
, the
pressure decreases
.
Pressure equals to Force/Area
SI Unit for Pressure is
- Pascal (Pa) - newton per square metre (N/m²)
Pressure in Everyday Life
Disadvantages
Large force of the hammer exerts a large pressure on the finger, causing a bruise.
The sharp tip of the nail exerts a large pressure on car tyres.
The small areas of stiletto heels produce large pressure on floor and leave unsightly marks on carpets.
Advantages
The sharp tip of a pin exerts a large pressure on noticeboards.
The sharp edge of a knife blade exerts a large pressure on food.
The spikes on football shoes exert a large pressure on the
ground.
Pressure in Liquids
When an object is immersed in a liquid, the liquid exerts
pressure on it.
The deeper the object is immersed, the
greater the liquid pressure.
Dams
Water pressure is higher at the base of the dam thus the
base has thicker wall than its top.
Submarines
Submarines dive to great depths underwater. The pressure deep below the water surface can be very high. A submarine needs a strong body to withstand high pressure.
If the submarine dives beyond its depth limit, the pressure may become too high and damage its physical structure.