3.2 Making Things Work Flashcards

1
Q

Define moments?

A

The turning effect of a force is called its moment

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2
Q

What makes it easier to move something in moments? Why?

A

A longer bar:
Less force is needed
Or
Increases the moment for the same force applied

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3
Q

What is the principle of moments?

A

The sum of the clockwise moments = the sum of the anticlockwise moments

If the lever is balanced

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4
Q

What is the centre of mass?

A

The point where the mass is thought to be the most concentrated

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5
Q

Where is the centre of mass when an object is freely suspended?

A

Directly below the point of suspension - the object is in equilibrium

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6
Q

How do you find the centre of mass of an object?

A

Attach the clamp to the stand, place a steel rod through the clamp horizontally
Hang the object by the rod through one hole so it is free to swing (no obstruction)
Hang a plumb line from same suspension point
Mark the vertical line the plumb line has created on the shape with a pen and a ruler
Repeat with at least two other hole
The point where the lines cross is the centre of mass

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7
Q

Where is the centre of mass for a symmetrical object?

A

Along the axis of symmetry

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8
Q

What is the line of action?

A

An imaginary perpendicular vertical line from the centre of mass to the ground

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9
Q

What happens to an object if the centre of mass is inside the base?

A

It is stable
Doesn’t fall over
Either the clockwise or anticlockwise moment is greater than the other

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10
Q

What happens to an object if the centre of mass is directly on the pivot?

A

It is stable

The moments are balanced

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11
Q

What happens to an object if the centre of mass is outside the base?

A

It is unstable
Falls over
Either the clockwise or anticlockwise moment is greater than the other

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12
Q

What factors allow for a strong stability?

A

Low centre of mass
Wider base
Line of action from the COM
surface area of an object

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13
Q

What property of liquids is known in hydraulics?

A

They are virtually incompressible

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14
Q

What is the pressure like in a hydraulic system?

A

Pressure in a liquid is transmitted equally in all directions

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15
Q

A force exerted at one point on a liquid…

A

Will be transmitted to all other points in the liquid

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16
Q

What links all the forces and areas together?

A

F1 F2
— = —
A1 A2

17
Q

What does a larger area of the slave allow?

A

The force is multiplied at he other end as the pressure is the same throughout

18
Q

What properties does an object have when moving in a circle?

A

It continuously changes direction
Therefore
Continuously changes velocity

19
Q

If an object moving in a circle is going at a constant speed why is it accelerating?

A

It is constantly changing velocity therefore it still accelerates

20
Q

What is the acceleration in a circular motion called?

A

The centripetal acceleration

21
Q

What is centripetal force?

A

The resultant forces acting on the object in a circular motion

22
Q

What is strange about centripetal force?

A

It doesn’t exist is it’s own right but is provided by the action of other forces

23
Q

Examples of centripetal forces being created as a result of:

A

Conker on a string: result of tension
Vehicle turning a corner: friction between tyres and road
Planets orbiting the sun: gravity

24
Q

What factors mean the centripetal force increases?

A

Increased mass of object
Increased speed of object
Decreased radius of circle

25
Q

What happens if you let go of an object currently moving in a circular motion?

A

It will fly off in a straight line

26
Q

What is an oscillating motion?

A

The motion of the pendulum moving to and fro along the same line

27
Q

What is the equilibrium position of a pendulum?

A

The position of the bob when it stops moving

28
Q

What factor affects oscillating motion of the pendulum?

A

Length of the pendulum
Or
It’s equilibrium position

29
Q

What is the amplitude of an oscillating object?

A

The distance it moves from the equilibrium position to the highest point (either side)

30
Q

What is the time period of a pendulum?

A

The time taken for one cycle

A to B to A again

31
Q

What is the frequency of oscillation of a pendulum?

A

The number of complete cycles of oscillation per second

32
Q

As the length of the pendulum increases…

A

The time period increases

33
Q

What is frequency measured in?

A

Hertz

Hz