Forces Flashcards
(53 cards)
1
Q
In pulley questions, what should you say if they ask state how you have used the fact that the string is inextensible
A
all particles have acceleration of same magnitude
2
Q
A
a) a = g/9
T = 40mg/9
b) all particles have acceleration of same magnitude
Solution for part c
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4
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6
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8
Q
What about if it asked for between -j
A
Angle same as you should make j the adjacent
9
Q
How many kilogram is 6 tonnes
A
6,000 kg
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11
Q
How does a pulley show that it is smooth
A
Tension is same on both sides of pulley
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21
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How do you show that light is being inextensible
Say all particles have same acceleratiom
28
What would happen if coefficient of friction is higher than a number it should be
System would remain in equilbrium
29
Identify one limitation of model
Just mention dimensions of ball and dimensions of string
Don't talk about gravity unless it gives you a value of gravity that's rounded too a limited number of significant figures
30
Don't simplify T even though you know the value, always include in the equation
31
For part b) once Q hits ground Acceleration treated as normal for horizontal as it becomes zero
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For part b, once Q hits the ground, Acceleration for P is just gravity going downards, hence it goes down to instantaneous rest
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Only part c
Resistance is not constant
36
Got wrong originally because you said 1+c/2 = 3c/2 which is obviously not mathematically correct
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u = 1/4
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Let's say you have calculated acceleration of a pulley system for one of the particles. How would your answer change if the string became not light
Tensions of two equations of motion would be different
Tension of A and B would be different
So acceleration in system would not be constant
44
When being asked to write equation of motion what should you do
Include all factors, if you can find friction still make an equation where you simply include friction not as an actual number
45
You found the tension but you didnt round so a mark was dropped. You knew how to do part c but kept chasing to get an actual value hence you didn't do part c and dropped marks. Please just do it
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If ladder was not modelled as uniform, state how this would affect the calculated value of u (coefficient of friction)
position of centre of mass affects value of reaction force acting on ground. If centre of mass is closer to A (point on ground) u is smaller and vice versa
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