Unit 1 Flashcards
1
Q
Density
A
Density = Mass / Volume
2
Q
Uptrust
A
- Weight of fluid displaced (Archimedes principle)
- Upthrust = g · volume (of object / fluid displaced)· density (fluid)
3
Q
Stoke’s Law
A
- F (N) = 6πηrv(ms
- Drag force = 6 · π · viscosity (Pas) · radius (m) · velocity(ms⁻¹)
- Object must be spherical
- Flow must be laminar
4
Q
Viscosity of fluids
A
- Liquids: As temperature increases, viscosity decreases
- Gases: As temperature increases, so does viscosity
5
Q
Laminar flow
A
- Fluid layers flow parallel to each other and don’t interact
- Constant speed
6
Q
Turbulent flow
A
- Fluid layers can cross over each other and turn at angles
- Eddy currents are formed
- Variable speed
7
Q
Hook’es law
A
- ΔF (N) = k (Nm⁻¹) · Δx (m)
- Proportionality between the force applied and extension of spring until the limit of proportionality
8
Q
Work done (Hooke’s Law)
A
- Area under graph
- Work done (J) = 1/2 · k · (Δx)²
9
Q
Stress
A
- Stress (Pa) = Applied froce (N) / Cross-sectional area (m²)
- A measure of the force in the cross-sectional area of a sample
10
Q
Strain
A
Strain = extrension (m) / original length (m)
- Measure of extension/compression of a sample in rearliton to original size
11
Q
Young modulus
A
Young modulus (Pa) = stress (Pa) / strain
- Measure of the stiffness of a material
12
Q
Thermal transfer of energy
A
- The thermal energy released when unloading a spring
- Work done (load) - Work done (unload)
13
Q
Elastic deformation
A
- Sample returns to original extension after force removed
14
Q
Plastic deformation
A
- Sample does not returns to original extension after force removed
15
Q
2 identical springs in series
A
- Overall k, half of k of single spring
- Double the extension with same load
16
Q
2 identical springs in series
A
- Overall k, double of k of single spring
- Half the extension with same load
17
Q
Limit of proportionality
A
- Load at which Hooke’s law stops beign obeyed
- Returns to original shape
18
Q
Elastic limit
A
- Load at which the material won’t return to original extension
19
Q
Yield point
A
- Molecular change in material, causing a decrease in stres
20
Q
Ultimate tensile strength
A
- Measure of the load that can be applied to a material before it fails
21
Q
Breaking point
A
- Load at which the material breaks
22
Q
Moment
A
- Turning effect of force
- Moment (Nm) = Force (N) · Perpendicular distance from pivot (m)
- Clockwise or anticlockwise
23
Q
Centre of gravity
A
- The point through which the entire weight acts
- Low centre of gravity -> higher stability
24
Q
Momentum
A
- Momentum (Kgms⁻¹) = Mass (Kg) · Velocity (ms⁻¹)
25
Impulse
- Force applied (N) = ΔMomentum (Kgms⁻¹) / ΔTime (s)
- Impulse (Ns⁻¹) = Force (N) · ΔTime (s)
26
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
27
Resultant Force
- A single force that has the same effect as all individual forces combined
28
Vectors
- Represented with arrows
- Arrow length and direction represent magnitude and direction of force
29
Vector addition
- Place vectors head to tail
- Resultant force is line formed from first tail to last head
30
Newton's frist law
- A body remains at constant velocity until acted by a non-zero resultant force
31
Newton's second law
- F = ma
32
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
33
Weight
- Force due to gravity, polling on each kilogram of mass depending on local gravitation field strength
34
Mass
- Amount of matter in a body
35
Gravitation field strength
- Gravitation force a body exerts at a certain position on each kilogram of mass
- NKg⁻¹ / ms⁻²
36
Principle of conservation of energy
- Energy can't be created or destroyed, only transferred from one from to another
37
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
