Unit 1 Flashcards
Density
Density = Mass / Volume
Uptrust
- Weight of fluid displaced (Archimedes principle)
- Upthrust = g · volume (of object / fluid displaced)· density (fluid)
Stoke’s Law
- F (N) = 6πηrv(ms
- Drag force = 6 · π · viscosity (Pas) · radius (m) · velocity(ms⁻¹)
- Object must be spherical
- Flow must be laminar
Viscosity of fluids
- Liquids: As temperature increases, viscosity decreases
- Gases: As temperature increases, so does viscosity
Laminar flow
- Fluid layers flow parallel to each other and don’t interact
- Constant speed
Turbulent flow
- Fluid layers can cross over each other and turn at angles
- Eddy currents are formed
- Variable speed
Hook’es law
- ΔF (N) = k (Nm⁻¹) · Δx (m)
- Proportionality between the force applied and extension of spring until the limit of proportionality
Work done (Hooke’s Law)
- Area under graph
- Work done (J) = 1/2 · k · (Δx)²
Stress
- Stress (Pa) = Applied froce (N) / Cross-sectional area (m²)
- A measure of the force in the cross-sectional area of a sample
Strain
Strain = extrension (m) / original length (m)
- Measure of extension/compression of a sample in rearliton to original size
Young modulus
Young modulus (Pa) = stress (Pa) / strain
- Measure of the stiffness of a material
Thermal transfer of energy
- The thermal energy released when unloading a spring
- Work done (load) - Work done (unload)
Elastic deformation
- Sample returns to original extension after force removed
Plastic deformation
- Sample does not returns to original extension after force removed
2 identical springs in series
- Overall k, half of k of single spring
- Double the extension with same load
2 identical springs in series
- Overall k, double of k of single spring
- Half the extension with same load
Limit of proportionality
- Load at which Hooke’s law stops beign obeyed
- Returns to original shape
Elastic limit
- Load at which the material won’t return to original extension
Yield point
- Molecular change in material, causing a decrease in stres
Ultimate tensile strength
- Measure of the load that can be applied to a material before it fails
Breaking point
- Load at which the material breaks
Moment
- Turning effect of force
- Moment (Nm) = Force (N) · Perpendicular distance from pivot (m)
- Clockwise or anticlockwise
Centre of gravity
- The point through which the entire weight acts
- Low centre of gravity -> higher stability
Momentum
- Momentum (Kgms⁻¹) = Mass (Kg) · Velocity (ms⁻¹)
Impulse
- Force applied (N) = ΔMomentum (Kgms⁻¹) / ΔTime (s)
- Impulse (Ns⁻¹) = Force (N) · ΔTime (s)
Principle of conservation of momentum
- Initial momentum = Final momentum
- Momentum of a asystem remains constant
- In elastic collisions: KE is conserved
- Non-elastic collisions: KE isn’t conserved
Resultant Force
- A single force that has the same effect as all individual forces combined
Vectors
- Represented with arrows
- Arrow length and direction represent magnitude and direction of force
Vector addition
- Place vectors head to tail
- Resultant force is line formed from first tail to last head
Newton’s frist law
- A body remains at constant velocity until acted by a non-zero resultant force
Newton’s second law
- F = ma
Newton’s third law
-When a body exerts a force on another body , the seconda object exerts an equal, opposity force on the first body
- All forces come in action-reaction paris of the same type
Weight
- Force due to gravity, polling on each kilogram of mass depending on local gravitation field strength
Mass
- Amount of matter in a body
Gravitation field strength
- Gravitation force a body exerts at a certain position on each kilogram of mass
- NKg⁻¹ / ms⁻²
Principle of conservation of energy
- Energy can’t be created or destroyed, only transferred from one from to another
Constant speed down a slope
- KE is conserved
- GPE decreases as height decreases
- Lost GPE is transferred to its surroundings as thermal energy as the body does work against friction/drag
