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# Unit 5 Physics Edexcel A2 and Edexcel IAL

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1. Attachment 531921531923
can someone explain the mark scheme for me please? I am confused because if water were to have its own centripetal force (which acts towards the center) wouldn't it fall right outta the bucket?
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2. (Original post by O\$car)

Attachment 531921531923
can someone explain the mark scheme for me please? I am confused because if water were to have its own centripetal force (which acts towards the center) wouldn't it fall right outta the bucket?
Treat the water and bucket as a body.
Since bucket has force on water (reaction) it falls out when R=0 right so we need R>=0 at top(where there is minimum speed) hence giving the minimum required speed for reaction to be greater then zero.

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3. (Original post by physicsmaths)
Treat the water and bucket as a body.
Since bucket has force on water (reaction) it falls out when R=0 right so we need R>=0 at top(where there is minimum speed) hence giving the minimum required speed for reaction to be greater then zero.

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thats like the part i don't understand why are you treating the water and the bucket as one system :?
4. (Original post by O\$car)
thats like the part i don't understand why are you treating the water and the bucket as one system :?
Because water+bucket are in circular motion.

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5. (Original post by physicsmaths)
Because water+bucket are in circular motion.

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But if you treat them as a single body then the bucket wouldn't be exerting reaction force on water since they are the same body
6. (Original post by O\$car)
But if you treat them as a single body then the bucket wouldn't be exerting reaction force on water since they are the same body
But the overall forces on the body is still the weight of it all which is the min centripetal force.

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7. (Original post by physicsmaths)
But the overall forces on the body is still the weight of it all which is the min centripetal force.

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yes i get that bit

the part i don't understand is whats inside the bracket of the first marking point, in order for water not to fall out the reaction force has to be larger than the weight of water. So the direction of force would be away from centre of circle, so it wouldn't be a centripetal force. If there is a centripetal force, then that means that the resultant force points toward the centre of circle, which would cause water to fall out.
8. (Original post by O\$car)
yes i get that bit

the part i don't understand is whats inside the bracket of the first marking point, in order for water not to fall out the reaction force has to be larger than the weight of water. So the direction of force would be away from centre of circle, so it wouldn't be a centripetal force. If there is a centripetal force, then that means that the resultant force points toward the centre of circle, which would cause water to fall out.
Draw a force diagram. R+mg=mv^2/r (since in motion) we require R>=0
mv^2/r>=mg giving the required minimum speed
The water is in circular motion with its body having forces if its weight and reaction from contact with bucket.

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9. I recommend that everyone does some brief revision on unit 1 and 2. They often ask questions that are straight from the unit 1 or 2 specification, usually unit 2.
10. (Original post by mrbeady9)
I recommend that everyone does some brief revision on unit 1 and 2. They often ask questions that are straight from the unit 1 or 2 specification, usually unit 2.
They like to surprise you with materials definitions in Unit 5 sometimes, mainly toughness, hardness and strength.
11. Looking at chem and biology ial unit 6 as both came considerably harder. Are you guys worried about physics unit 6?

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12. (Original post by usmanzubair)
Looking at chem and biology ial unit 6 as both came considerably harder. Are you guys worried about physics unit 6?

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[/QUOTE]

Isn't Unit 6 the CW? I already done that.
13. Isn't Unit 6 the CW? I already done that.[/QUOTE]

this is an IAL thread not GCE
14. (Original post by usmanzubair)
Isn't Unit 6 the CW? I already done that.
this is an IAL thread not GCE [/QUOTE]

No it isn't, it's for both. It was set up by someone doing GCE, and they included IAL in the title since the content is identical so there's not really a need for a separate thread for it. Easy mistake to make though
15. (Original post by samb1234)
this is an IAL thread not GCE
No it isn't, it's for both. It was set up by someone doing GCE, and they included IAL in the title since the content is identical so there's not really a need for a separate thread for it. Easy mistake to make though[/QUOTE]

Hm sure no doubt. But I am asking to IAL students what they think about phy unit 6 (IAL) difficulty comparing unit 6 bio and chem (IAL) both were considerably harder this session.

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16. (Original post by 16characterlimit)
They like to surprise you with materials definitions in Unit 5 sometimes, mainly toughness, hardness and strength.
Thanks, I haven't seen it come up yet, but I will be sure to revise it. Could you tell me the year of the paper it came up in?
17. (Original post by mrbeady9)
Thanks, I haven't seen it come up yet, but I will be sure to revise it. Could you tell me the year of the paper it came up in?
https://a4942901ab27cf2817f7a4f7497d...%20Physics.pdf

Q 16

https://a4942901ab27cf2817f7a4f7497d...%20Physics.pdf

Q 18

It also definitely came up during a multiple choice, but I couldn't find it.
18. (Original post by 16characterlimit)
https://a4942901ab27cf2817f7a4f7497d...%20Physics.pdf

Q 16

https://a4942901ab27cf2817f7a4f7497d...%20Physics.pdf

Q 18

It also definitely came up during a multiple choice, but I couldn't find it.
Much appreciated!
19. Here are the Unit 1 Materials definitions:

Ultimate tensile strength / Breaking stress
Maximum stress before a material is pulled apart

Brittle
A material that shows no plastic deformation just beyond its elastic limit

Compressive force
A force applied to a material that causes compression or extension

Compressive strain
Amount of deformation per unit length of a material (ε=Δx/x) (unitless)

Compressive stress
The compressive force per unit area (σ= F/A) (Nm-2)

Density
Mass per unit volume (p=m/V) (kgm-3)

Ductile
A material that shows plastic deformation before fracturing under tension A ductile material can be pulled into wires, or threads e.g. Copper.

Elastic limit
Load on a spring beyond which the extension increases more rapidly than
expected hence the spring remains permanently deformed when the load is removed (elastic deformation ends)

Elastic deformation
Deformation after which the force is no longer applied the material will return to its original shape

Hard
Materials that resist plastic deformation by surface indentation or scratching e.g. diamond

Laminar flow / streamline flow
Smooth fluid flow in which parallel layers have a constant velocity

Limit of proportionality
Stress is proportional to strain up to this point

Malleable
Materials that show a large plastic deformation under compression. These materials can be beaten into sheets e.g. gold

Stiff
Steep gradient of a force-extension graph - High Young modulus

Stiffness
Measure of the resistance of a material to deformation by tensile force.

Strength
Ability of a material to withstand stress

Tensile strain
Extension per unit length of a material subjected to a tensile force.

Archimedes’ Principle
Upthrust is equal to weight of displaced fluid (u=Vpfg)

Fluid
A substance that can flow – usually with reference to a gas or liquid, but sometimes solids

Viscosity
A measure of afluid's resistance to gradual deformation – inversely proportional to flow rate

Viscous drag / Stokes Force
Friction acting against movement in a fluid

Flow rate Volume of fluid that passes per second (m3s-1) (Q=V/t)

Terminal velocity
Highest attainable velocity in free fall, it occurs when weight is equal to upthrust and Stokes’ Force combined (W=u+F)

Elastic potential energy
Energy stored due to a load causing deformation (Eel=½FΔx) (Area underneath force-extension graph)

Young’s Modulus
Measure of the stiffness of an elastic material
The ratio of the stress to the strain along where Hooke's law holds (linear line)
Attached Files
20. UNIT 1 - Mechanics & Materials key terms.docx (16.7 KB, 20 views)
21. Does anyone have any tips/methods on getting the marks for the written questions. Half the time the mark scheme wants things the question doesn't ask for and the other half they are incredibly nitpicky and I find myself writing the entire do not credit/ignore/reject section.

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