1.28 Flip the axis!
08 November 2011
08:41
· Graphs for wires and springs look the same - initial region obeys Hooke's Law
· Elastic bands do not obey Hooke's Law
1.26 Answer
31 October 2011
17:36
1.26 Question
31 October 2011
17:36
· 1.26 understand that the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam
Question
· The Newtonmeters in the diagram labelled L and R are spaced 1m apart
· The hanging mass has a weight of 7N and is placed 0.3m from the Newtonmeter labelled R
· What are the readings on Newtonmeters L and R?
Hints to help
· Calculate moments about either of the Newtonmeters; moments should be balanced because the beam is stationary
· Now calculate moments about the other Newtonmeter
· You should now have found the readings on each Newtonmeter; is there a way to check that these answers are correct?
Fa x da = Fc x dc
7 x 0.3 = Fc x 1.0
2.1N= Fc
Fa x da = Fc x dc
7 x 0.7 = Fa x 1.0
4.9N = Fa
The reading on the Newton meter R will be 2.1N
The reading on Newton meter Lwill be 4.9N
1.25 Principle of Moments Questions
29 September 2010
14:37
|
Size of load (tonnes) |
Size of load (N) |
Maximum length of jib (m) |
Moment (load x length) |
|
10 |
100,000 |
12 |
1,200,000 |
|
20 |
200,000 |
6 |
1,200,000 |
|
30 |
300,000 |
4 |
1,200,000 |
|
40 |
400,000 |
3 |
1,200,000 |
5b) All of the moments are the same, this is because the highest moment the crane can extend to is 1,200,000.
c. M= F x d, M=1,200,000, d=24m, F= 1,200,000/24, F=50,000N
4a) X=20N
b) Y=4N
c) Z=1N
1.23 Moments Questions
29 September 2010
14:37
PFY p106
2a) this means that the mechanic will have to apply less force to undo a tight nut, as he is further away from the pivot.
b) This means that a person will have to apply less force to open the door, as the handle is far away from the pivot (hinge)
3. M=F x d, F=200N, d=20cm, M=200 x 20, M=4000Ncm
1.25 Starter
31 October 2011
12:12
· Why doesn't the see-saw balance?
Explanation
· The perpendicular distance from the pivot is the same on each side
· But the force (weight) on the left is great
· So the moment (turning force) on the left is greater
· The see-saw will rotate anticlockwise
1.25
Tuesday, July 06, 2010
3:04 PM
· 1.25 recall and use the principle of moments for a simple system of parallel forces acting in one plane
Principle of Moments
· When a system is balanced then the anticlockwise moments are equal to the clockwise moments
· This means that the anticlockwise turning force is equal to the clockwise turning force and the system doesn't move
Ma = Mc
Fa x da = Fc x dc
Ma = anticlockwise moment (Nm)
Fa = force causing the anticlockwise rotation (N)
da = perpendicular distance of Fa from the pivot (m)
Mc = clockwise moment (Nm)
Fc = force causing the clockwise rotation (N)
dc = perpendicular distance of Fc from the pivot (m)