3.2 Making Things Work Flashcards
Define moments?
The turning effect of a force is called its moment
What makes it easier to move something in moments? Why?
A longer bar:
Less force is needed
Or
Increases the moment for the same force applied
What is the principle of moments?
The sum of the clockwise moments = the sum of the anticlockwise moments
If the lever is balanced
What is the centre of mass?
The point where the mass is thought to be the most concentrated
Where is the centre of mass when an object is freely suspended?
Directly below the point of suspension - the object is in equilibrium
How do you find the centre of mass of an object?
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
Where is the centre of mass for a symmetrical object?
Along the axis of symmetry
What is the line of action?
An imaginary perpendicular vertical line from the centre of mass to the ground
What happens to an object if the centre of mass is inside the base?
It is stable
Doesn’t fall over
Either the clockwise or anticlockwise moment is greater than the other
What happens to an object if the centre of mass is directly on the pivot?
It is stable
The moments are balanced
What happens to an object if the centre of mass is outside the base?
It is unstable
Falls over
Either the clockwise or anticlockwise moment is greater than the other
What factors allow for a strong stability?
Low centre of mass
Wider base
Line of action from the COM
surface area of an object
What property of liquids is known in hydraulics?
They are virtually incompressible
What is the pressure like in a hydraulic system?
Pressure in a liquid is transmitted equally in all directions
A force exerted at one point on a liquid…
Will be transmitted to all other points in the liquid
What links all the forces and areas together?
F1 F2
— = —
A1 A2
What does a larger area of the slave allow?
The force is multiplied at he other end as the pressure is the same throughout
What properties does an object have when moving in a circle?
It continuously changes direction
Therefore
Continuously changes velocity
If an object moving in a circle is going at a constant speed why is it accelerating?
It is constantly changing velocity therefore it still accelerates
What is the acceleration in a circular motion called?
The centripetal acceleration
What is centripetal force?
The resultant forces acting on the object in a circular motion
What is strange about centripetal force?
It doesn’t exist is it’s own right but is provided by the action of other forces
Examples of centripetal forces being created as a result of:
Conker on a string: result of tension
Vehicle turning a corner: friction between tyres and road
Planets orbiting the sun: gravity
What factors mean the centripetal force increases?
Increased mass of object
Increased speed of object
Decreased radius of circle
What happens if you let go of an object currently moving in a circular motion?
It will fly off in a straight line
What is an oscillating motion?
The motion of the pendulum moving to and fro along the same line
What is the equilibrium position of a pendulum?
The position of the bob when it stops moving
What factor affects oscillating motion of the pendulum?
Length of the pendulum
Or
It’s equilibrium position
What is the amplitude of an oscillating object?
The distance it moves from the equilibrium position to the highest point (either side)
What is the time period of a pendulum?
The time taken for one cycle
A to B to A again
What is the frequency of oscillation of a pendulum?
The number of complete cycles of oscillation per second
As the length of the pendulum increases…
The time period increases
What is frequency measured in?
Hertz
Hz
