βοΈβπ₯ β’ Lesson 3.2 : Effect of Forces (Phys) Flashcards
Letβs dig a little bit deeper into the effects of forces, friction, turning effects, the centre of gravity, and the understanding of energy, work, power and pressure.
What changes can forces produce in an object?
Forces can change an objectβs size, shape, or motion.
How do you determine the resultant force along a straight line?
Add forces acting in the same direction, subtract forces acting in opposite directions.
What is friction?
Friction is a force between two surfaces that resists motion and produces heat.
What is drag?
Drag is friction acting on an object moving through a liquid or gas.
What is air resistance?
Air resistance is the friction (drag) force acting on an object moving through air.
What happens to an object if there is no resultant force?
It stays at rest or moves in a straight line at constant speed.
What is Newtonβs Second Law?
Force equals mass times acceleration (F = ma).
The force and acceleration are in the same direction.
How do you interpret a loadβextension graph for an elastic solid?
The graph shows how an objectβs extension changes with applied force.
What is the spring constant?
The spring constant (k) is force per unit extension.
Equation: k = f/x
F = Force applied to the spring (In Newtons, N)
X = Extension of the spring (in meters, m)
What is the limit of proportionality in a loadβextension graph?
The point where extension is no longer directly proportional to force.
What is the moment of a force?
The moment of a force is its turning effect around a pivot. It is calculated as:
Moment = Force Γ Perpendicular distance from the pivot
How do you apply the principle of moments to balance a beam?
Clockwise moment = Anticlockwise moment
This means: (Force Γ Distance) on one side = (Force Γ Distance) on the other side.
What does it mean when an object is in equilibrium?
An object is in equilibrium when it has no resultant force (it stays still or moves at a constant speed), and no resultant moment (it doesnβt rotate).
What is the centre of gravity?
The centre of gravity is the point where an objectβs weight appears to act.
For regular shapes:
β’ Rectangular block β Center of the block
β’ Sphere β Center of the sphere
β’ Cylinder β Middle of its height
How do you find the centre of gravity of an irregular lamina?
- Hang the lamina from a point and let it settle.
- Draw a vertical line down from where it hangs.
- Repeat from another point.
- The intersection of the lines is the centre of gravity.
How does the centre of gravity affect stability?
A lower centre of gravity = more stable (ex. race cars).
A higher centre of gravity = less stable (ex. tall objects fall easily).
What are the different ways energy can be stored?
Kinetic (moving objects), GPE (height), chemical (batteries, food), elastic (stretched springs), nuclear (inside atoms), electrostatic (charges), thermal (heat).
How is Energy Transferred?
- By forces β Mechanical work (pushing, lifting, stretching)
- By electricity β Work done in circuits
- By heating β Conduction, convection, radiation
- By waves β Electromagnetic, sound
Kinetic Energy Formula
Ek = Β½ mvΒ²
β’ m = mass (kg)
β’ v = velocity (m/s)
Gravitational Potential Energy Formula
ΞEp = mgΞh
β’ m = mass (kg)
β’ g = 9.8 N/kg (Earth)
β’ Ξh = height change (m)
What is the principle of conservation of energy?
Energy cannot be created or destroyed, only transferred between stores.
Total energy before = Total energy after
Work Done Formula?
W = Fd = ΞE
β’ F = force (N)
β’ d = distance moved (m)
β’ Work done = energy transferred
How can you obtain energy from fossil fuels?
Name advantages and disadvantages.
Process: Combustion in power plants
Energy: Heat energy β water β steam β turbine β generator β electrical power
Advantages: Reliable, high power output
Disadvantages: Non-renewable, high environmental impact (COβ emissions)
How can you obtain energy from biofuels?
Name advantages and disadvantages.
Process: Burning of organic materials (wood, crops, waste)
Energy: Chemical energy β combustion β steam β turbine β generator β electrical power
Advantages: Renewable, reduces waste
Disadvantages: Land use, deforestation, emissions
How can you obtain energy from water (hydropower)?
Name advantages and disadvantages.
Hydroelectric dams: Water falls, spins turbines
β’ Tidal: Uses ocean tides
β’ Wave: Uses ocean waves
Advantages: Renewable, reliable
Disadvantages: Environmental impact, limited locations
How can you obtain energy from geothermal resources?
Name advantages and disadvantages.
Process: Heat from Earthβs core β steam β turbine β generator β electrical power
Advantages: Renewable, low emissions
Disadvantages: Location-dependent, high initial costs
How can you obtain energy from nuclear fission?
Name advantages and disadvantages.
Process: Splitting of atoms (Uranium) β heat β steam β turbine β generator β electrical power
Advantages: High power, low emissions
Disadvantages: Waste disposal, risk of accidents
How can you obtain energy from solar cells?
Name advantages and disadvantages.
Process: Sunlight β solar panels β electrical power
Advantages: Renewable, low environmental impact
Disadvantages: Intermittent, location-dependent
How can you obtain energy from solar thermal collectors?
Name advantages and disadvantages.
Process: Sunlight β heating of water β energy storage
Advantages: Renewable, low emissions
Disadvantages: Only works in sunny regions, intermittent
How can you obtain energy from wind?
Name advantages and disadvantages.
Process: Wind β turbine β generator β electrical power
Advantages: Renewable, low emissions
Disadvantages: Intermittent, location-dependent
What is the main source of energy for all (except geothermal, nuclear and tidal)?
The Sunβs radiation.
What is nuclear fusion and how does it release energy?
Nuclear fusion is the process where hydrogen atoms fuse together to form helium, releasing large amounts of energy.
This process powers the Sun.
What is nuclear fission and how does it release energy?
Nuclear fission is the process where heavy atoms (like Uranium) are split into smaller atoms, releasing a significant amount of energy.
This is used in nuclear power plants.
How do you calculate the efficiency of energy transfer using useful energy output and total energy input?
Efficiency = (Useful energy output / Total energy input) Γ 100%
How do you calculate the efficiency of energy transfer using power output and power input?
Efficiency = (Useful power output / Total power input) Γ 100%
How do you define power in terms of work done?
Power is the rate at which work is done. The equation is:
P = W/t (Power = Work done / Time)
How do you define power in terms of energy transferred?
Power is the rate at which energy is transferred. The equation is:
P = ΞE/t (Power = Change in Energy / Time)
How does pressure vary with force and area in everyday examples?
Pressure increases when the force is greater or the area is smaller.
For example, a sharp object exerts more pressure than a blunt object
How is pressure defined in terms of force and area?
Pressure is the force applied per unit area. The equation is:
p = f/a (Pressure = Force / Area)
