Unit 1 - Motion, forces and energy Flashcards
Common units of length
mm, cm, m, km
Common units of time
ms, s, min, h, d
Common units of volume
cm^3, m^3
Period
The time taken for a full oscillation (start - start)
Vectors
Measurements that have specific direction and magnitude
Scalars
Measurements that have magnitude but no specific direction in which they act
Scalar examples
- Time
- Speed
- Pressure
- Distance
- Mass
- Energy
Vector examples
- Velocity
- Displacement
- Momentum
- Weight
- Acceleration
- Force
Average speed calculation
Average speed(m/s) = Total distance travelled(m) ÷ Total time taken(s)
Velocity
The speed of an object in a specific direction
Acceleration
The change in velocity per unit time
Deceleration/negative acceleration
The negative change in velocity per unit time
Acceleration calculation
Acceleration(m/s^2) = Change in velocity (m/s) ÷ time taken (s)
Notation for deceleration
- Negative acceleration e.g. -2m/s^2
Speed
The change in distance travelled per unit time
Displacement
How far an object is from its starting position in a particular direction
Features of a distance-time graph
- Straight sloping line = constant speed
- Straight loping line of higher gradient = faster constant speed
- Flat/horizontal line = stationary
- Gradient = Speed
Features of a speed-time graph
- Flat horizontal line at zero speed = stationary
- Flat horizontal line above zero speed = constant speed
- Upward sloping line = acceleration - steeper gradient = higher acceleration
- Downward sloping line = deceleration
- Gradient = acceleration
Figure for acceleration of gravity/acceleration of free fall
g = 9.8m/s^2
Calculating distance travelled on a speed-time graph
Calculate the area under the line
Relationship with air resistance and acceleration
- More air resistance = less acceleration
- More acceleration = more air resistance
Terminal velocity
The ‘top speed’ of any object when falling
When terminal velocity occurs
When the downward force of weight is balanced by air resistance
Weight
A gravitational force on an object that has mass
Unit of weight
Newtons
Mass
The quantity of matter in an object at rest
Unit of mass
Kg
Gravitational field strength calculation
Gravitational field strength (N/Kg) = Weight(N) ÷ Mass(Kg)
Unit of gravitational field strength
9.8N/Kg - every 1 kg of mass is pulled downwards with the force of 9.8N
Gravitational field
A volume of space around where any mass would experience a force
Density calculation
Density (Kg/m^3) = Mass (Kg) ÷ Volume (m^3)
Density of water
- 1g/cm^3
- Density > 1g/cm^3 will sink
- Density < 1g/cm^3 will float
How forces can affect am object
- Change its shape
- Change its size
- Change its velocity
- Change its direction of motion
Friction
Impeded motion and results in heating
Calculating forces
- Forces acting in the same direction = addition
- Forces acting in opposing directions = subtraction for resultant force
Result of unbalanced forces
- Resultant force –> change in speed
Result of balanced forces
- No resultant force –> constant speed or stationary
Force calculation
Force (N) = Mass (Kg) x Acceleration (m/s^2)
Effects of more perpendicular force / situations needing more perpendicular force
- Mass of object increases
- Speed of object increases
- Radius of circle motion decreases
Need for an object to turn in a circle
A force to act perpendicular to motion
Hooke’s Law calculation
Force (N) = spring constant (N/m) x extension (m)
Limit of proportionality
The point at which when enough force is added, the spring deforms - seen as curve on spring constant graph
Moment
A turning force
Moment calculation
Moment (Nm) = Force (N) x perpendicular distance to the pivot (m)n
How to increase a moment
- Increase size of force
- Increase perpendicular distance from the pivot
Principle of moments
Total clockwise moment = total anti-clockwise moment
Equilibrium
No net moment / no resultant force forces or moments
Centre of gravity
The average position of all the mass in that object
Centre of gravity in regular shapes
Along the line of symmetry
Factors to stability
- Wide base
- Low centre of mass
Unstable
Center of gravity is not above the base
Momentum calculation
Momentum (Kg m/s) = Mass (Kg) x Velocity (m/s)
Factors to increases momentum
- Increase velocity
- Increase mass
Law of conservation of momentum
In any collision, the total momentum before and after the collision is the same
Impulse
Change in momentum
Impulse calculation
Final momentum - initial momentum
Impulse calculation 2
Impulse = Force x change in time
Force calculation (impulse)
Force = change in momentum/impulse ÷ change in time
Different types of energy
- Kinetic energy
- Chemical energy
- Nuclear energy
- Internal/thermal energy
- Electrostatic energy
- Elastic energy
- Gravitational potential energy
Principle of conservation of energy
Energy cannot be created or destroyed, only converted from one store to another
Kinetic energy equation
Kinetic energy (J) = 1/2 x mass (kg) x velocity (m/s)^2
Gravitational potential energy equation
Gravitation potential energy (j) = mass (kg) x acceleration of gravity (m/s^2) - 9.8 x change in height (m)
Work equation
Work done = energy transferred
Work done calculation
Work done (J) = Force (N) x distance moved in the direction of the force (m)
How electricity if generates
- Water boils into steam
- Stream turn a turbine that turns a generator making electricity
Nuclear energy
- Uses a nuclear reaction to produce heat
Hydroelectric energy
- Water rushing downstream through pipes and turbines to generate electricity
Tidal energy
Sea water trapped behind a dam wall to produce flow of water through turbines
Wave energy
Movement of waves up and down to produce electricity
Solar energy
- Solar panels absorb infrared electromagnetic waves to heat water
- solar cells produce electricity from the electromagnetic waves
Wind energy
Wind spins a turbine to make electricity
Geothermal energy
Water turns to steam due to heat of volcanic activity to spin a turbine
Three energy resources not originally from the sun
- Nuclear power
- Tidal power
- Geothermal power
Pros and cons of fossil fuels
Pros:
- High power output
- 24 hours a day output
- Cheap to build
Cons:
- Non-renewable
- Produces greenhouse gases
Pros and cons of nuclear energy
Pros:
- High power output
- 24 hours a day output
- No greenhouse gases
Cons:
- Non-renewable energy
- Radioactivity risks
- very expensive to build
Pros and cons of hydroelectric energy
Pros:
- Renewable resource
- No greenhouse gases
- High power output
Cons:
- Disrupts animal habitats ad displaces people
- Needs a big river
- Expensive to build
Pros and cons of tidal energy
Pros:
- Renewable resource
- No greenhouse gases
- High power output
Cons:
- Needs high tides - not common
- Blocks large area of the sea
- Expensive to build
Pros and cons of wave energy
Pros:
- Renewable resource
- No greenhouse gases
Cons:
- New technology - not reliable
- Low power output
Pros and cons of solar energy
Pros:
- Renewable resource
- No greenhouse gases
Cons:
- Unreliable - needs sunshine
- Low power output
- Expensive to build
Pros and cons of wind energy
Pros:
- Renewable resource
- No greenhouse gases
- Cheap to operate
Cons:
- Unreliable - needs wind
- Low power output per turbine
- Expensive to build
Pros and cons of geothermal energy
Pros:
- Renewable resource
- No greenhouse gases
- Reliable output
Cons:
- Only a few volcanic countries
- Relatively low power output
Efficiency energy calculation
Efficiency = Useful energy output ÷ energy input x 100%
Efficiency power calculation
Efficiency = Useful power output ÷ power input x 100%
Power calculation
Power (W) = energy transferred (J) ÷ Time taken (s)
Pressure equation
Pressure (Pa) = Force (N) ÷ Area (m^2)
Change in pressure equation
Change in pressure = Change in depth of liquid (m) x density of liquid (Kg/m^3) x gravitational field strength (N/Kg)
