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A Level OCR Physics > Chapter 6 - Materials > Flashcards

Chapter 6 - Materials Flashcards

1
Q

What is the name for forces that produce an extension in an object?

A

Tensile forces

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2
Q

What is the name for forces which compress an object?

A

Compressive forces

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3
Q

What happens to a spring when it experiences tensile and compressive forces?

A

Tensile deformation
Compressive deformation

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4
Q

What happens to the force-extension graph of a spring when it reaches its elastic limit? And what does the spring experience past this point?

A

It starts to flatten out and experience plastic deformation

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5
Q

What is elastic deformation?

A

When the shape of an object is deformed but it will still return to its original shape

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6
Q

What is plastic deformation?

A

When the shape of an object is deformed but it will not return to its original shape

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7
Q

When does a spring generally obey Hooke’s law?

A

When it has not yet reached its limit of proportionality.

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8
Q

What is the equation for force in terms of extension? (Hooke’s law)

A

Force = spring constant x extension

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9
Q

What is the spring constant of a spring actually measuring?

A

The stiffness of a spring

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10
Q

How can the spring constant be interpreted?

A

If the spring constant is high, the spring is difficult to extend

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11
Q

What is the gradient of a force - extension graph?

A

The spring constant

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12
Q

What happens to the work done on a material that is extended?

A

If it has not gone beyond its elastic limit, the work done on a material that is extended can be fully recovered

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13
Q

What is the equation for work done in a material that has been extended?

A

Change in W = Force x Change in distance

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14
Q

What is the area under a force - extension graph?

A

The work done on the spring

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15
Q

What is the work done on a spring in order to extend it transferred into?

A

Elastic potential energy within the spring

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16
Q

What is the equation for elastic potential energy and where has it come from?

A

E = 1/2 * F * extension
This is the area under a force extension graph since it will be a triangle

17
Q

What is the equation for elastic potential energy in terms of the spring constant?

A

E = 1/2 * k * extension^2

18
Q

What will doubling the extension of a spring do to its elastic potential energy? Why?

A

Multiply it by 4, since elastic potential energy is directly proportional to extension^2

19
Q

What is the name of the ‘loop’ formed under the force-extension graph of rubber?

A

A hysteresis loop.

20
Q

What does the area inside of a hysteresis loop represent?

A

The thermal energy released in the loading of the rubber material.

21
Q

What is the equation for tensile stress?

A

Stress = force / cross-sectional area

22
Q

What is the equation for tensile strain?

A

Strain = Extension / original length

23
Q

What is it called when a material is stretched and begins to get thinner?

A

Necking

24
Q

What are the 6 major points on a stress strain graph (for steel)? (In order)

A

The limit of proportionality
The elastic limit
Yield points 1 and 2
UTS point
Breaking point

25
Q

What is the limit of proportionality?

A

The point when a material stops obeying Hooke’s law

26
Q

What could define a strong material?

A

One with a high ultimate tensile strength

27
Q

What is the equation for young modulus?

A

Young modulus = Stress / strain

28
Q

When does the young modulus apply?

A

Up to the limit of proportionality of a material

29
Q

What is the unit for the young modulus?

A

Pa or Nm^-2

30
Q

How can you obtain the young modulus of a material from its stress strain graph?

A

By finding the gradient

31
Q

How can young modulus be interpreted?

A

A higher young modulus makes for a stiffer material

32
Q

How can you identify a brittle material from a stress strain graph?

A

A brittle material does not have a curve, the line simply ends when the material snaps

33
Q

What is the elastic limit?

A

The point at on a force-extension graph where if exceeded, a spring will no longer return to its original shape

34
Q

What is the equation for spring constant in a series of springs?

A

1/k = 1/k1 + 1/k2 (the same equation for resistance in parallel)

35
Q

What is the equation for spring constant for springs arranged in parallel?

A

K = k1 + k2

36
Q

What is the ultimate tensile strength of a material?

A

The maximum amount of stress it can endure before necking and breaking

37
Q

How can you measure the young modulus of a wire?

A

Stretch it between to points and mark its length at any point, then find the cross sectional area and total length of the wire. Then add weights to one end and as the wire stretches measured its new weight with each new mass added. Then calculate with this the stress and strain then the young modulus.

38
Q

What is the unit for stress?

A

Nm^-2

39
Q

What is the unit for strain?

A

There isn’t one

A Level OCR Physics (13 decks)

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