Lesson test: Internal forces

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Internal forces

1.[1p]
What does a positive bending moment do to a beam?

It sags it, stretching the bottom fibres and compressing the top ones

Correct

It hogs it, stretching the top fibres

The answer is: It sags it, stretching the bottom fibres and compressing the top ones

It twists it about its own axis

The answer is: It sags it, stretching the bottom fibres and compressing the top ones

It shortens it along its axis

The answer is: It sags it, stretching the bottom fibres and compressing the top ones

2.[2p]
A beam spans 6 m and carries 8 kN per metre over its whole length, on a pin and a roller. What is the maximum bending moment, in kN m?

CorrectNot quite: 36

3.[2p]
A cantilever 2.5 m long carries 8 kN per metre over its whole length. What is the magnitude of the bending moment at the built-in end, in kN m?

CorrectNot quite: 25

4.[2p]
A simply supported beam of span 10 m carries a single point load of 24 kN at midspan. What is the maximum bending moment, in kN m?

CorrectNot quite: 60

5.[2p]
Where on a beam does the maximum bending moment occur?

Where the shear force is zero or jumps through zero

Correct

Always at midspan

The answer is: Where the shear force is zero or jumps through zero

Where the distributed load is largest

The answer is: Where the shear force is zero or jumps through zero

At the supports, where the reactions act

The answer is: Where the shear force is zero or jumps through zero

6.[3p]
Match each loading feature to what it does to the diagrams.

A region with no load
A uniform distributed load
A concentrated point load
A concentrated couple

shear linear, moment parabolic
shear constant, moment linear
step in moment, no change in shear
step in shear, kink in moment

Show the answer

A region with no load: shear constant, moment linear A uniform distributed load: shear linear, moment parabolic A concentrated point load: step in shear, kink in moment A concentrated couple: step in moment, no change in shear

7.[2p]
The change in bending moment between two sections equals the area under the shear diagram between them.

True

Correct

False

The answer is: True

8.[3p]
A beam sits on a pin at one end and a roller 6 m away, then overhangs 2 m to a load at its free end. What happens at the pin?

The reaction acts downwards, so the support has to hold the beam down

Correct

The reaction is zero, because the overhang balances the span

The answer is: The reaction acts downwards, so the support has to hold the beam down

The reaction acts upwards and equals the load

The answer is: The reaction acts downwards, so the support has to hold the beam down

The reaction cannot be found without knowing the material

The answer is: The reaction acts downwards, so the support has to hold the beam down

9.[3p]
Which statements about shear and bending moment diagrams are correct?

Select all that apply

For a statically determinate beam they depend on the loads and geometry alone, not on the material

Correct

They cannot on their own say whether the beam is strong enough

Correct

The slope of the moment diagram at any point is the shear force there

Correct

A beam with a larger bending moment is always closer to failure than one with a smaller moment

The answer is: For a statically determinate beam they depend on the loads and geometry alone, not on the material, They cannot on their own say whether the beam is strong enough, The slope of the moment diagram at any point is the shear force there

1.[1p] What does a positive bending moment do to a beam?

2.[2p] A beam spans 6 m and carries 8 kN per metre over its whole length, on a pin and a roller. What is the maximum bending moment, in kN m?

3.[2p] A cantilever 2.5 m long carries 8 kN per metre over its whole length. What is the magnitude of the bending moment at the built-in end, in kN m?

4.[2p] A simply supported beam of span 10 m carries a single point load of 24 kN at midspan. What is the maximum bending moment, in kN m?

5.[2p] Where on a beam does the maximum bending moment occur?

6.[3p] Match each loading feature to what it does to the diagrams.

7.[2p] The change in bending moment between two sections equals the area under the shear diagram between them.

8.[3p] A beam sits on a pin at one end and a roller 6 m away, then overhangs 2 m to a load at its free end. What happens at the pin?

9.[3p] Which statements about shear and bending moment diagrams are correct?

1.[1p]
What does a positive bending moment do to a beam?

2.[2p]
A beam spans 6 m and carries 8 kN per metre over its whole length, on a pin and a roller. What is the maximum bending moment, in kN m?

3.[2p]
A cantilever 2.5 m long carries 8 kN per metre over its whole length. What is the magnitude of the bending moment at the built-in end, in kN m?

4.[2p]
A simply supported beam of span 10 m carries a single point load of 24 kN at midspan. What is the maximum bending moment, in kN m?

5.[2p]
Where on a beam does the maximum bending moment occur?

6.[3p]
Match each loading feature to what it does to the diagrams.

7.[2p]
The change in bending moment between two sections equals the area under the shear diagram between them.

8.[3p]
A beam sits on a pin at one end and a roller 6 m away, then overhangs 2 m to a load at its free end. What happens at the pin?

9.[3p]
Which statements about shear and bending moment diagrams are correct?