Using Physics To Make Things Work Flashcards
How do you increase the moment
Either the force must increase
Or the distance to the pivot must increase
Why is it easier to undo a wheel nut with a long spanner than a short one
The longer spanner increases the distance between the line of action of the force and the pivot
What is used to make a Job easier
A lever
What is the load
The weight of an object raised by a device used to lift the object or the force applied by a device when it is used to to shift an object
What is the effort
The force applied to a device used to raise a weight or shift an object
What does a lever act as
A force multiplier, so the effort we apply can be much less than the load
What’s a moment
The turning effect of a force
What are moments measured in
Newton metres
What is the line of action p
The line along which a force acts
What is a pivot
The point about which an object turns when acted on by a force that makes it turn
What is the centre of mass
The point where an objects mass may be thought to be concentrated
What is equilibrium
The state at which an object is as rest
How can you find the centre of mass of a thin irregular sheet of a material
Suspend the thin sheet from a pin held in a clamp stand. Because it is freely suspended, it is able to turn
When it comes to rest, hang a plumbline from the same pin
Mark the position of the plumbline against the sheet
Hang the sheet with the pin at another point and repeat the procedure
The centre of mass is where the lines that marked the position of the plumbline cross
What does the position of the centre of mass depend on
The shape of the object and it sometimes lies on the outside of the object
Where is the centre of mass for a symmetrical object
Along the axis of symmetry, if the object has many symmetry lines the centre of mass is where the lines of symmetry meet
If an object is in equilibrium it is …..
Balanced
If you take the moments at any point what will you find
The total clockwise moment and the total anti-clockwise moments are equal
What is the principle of moment
For an object in equilibrium, the sum of all the clockwise moments about any point = the sum of all the anti-clockwise moments about that point
What does the line of action of the weight of an object act through
The centre of mass
What is a resultant moment
The difference between the sum of the clockwise moments and the anti-clockwise moments about the same point if they are not equal
If the line of action of the weight lies outside the base of an object what happens
There will be a resultant moment and the object will topple over
The wider the base of an object and the lower its centre of mass……..
Further it has to tilt before the line of action of the weight moves outside the base
How is the stability of an object increased
Making its base widget and its centre of mass lower
What is pressure measured in
Pascals, Pa or N/m2
Liquids are ….
Virtually incompressible and the pressure in a liquid is transmitted equally in all directions
A force exerted on a liquid …..
Will be transmitted to other points in the liquid
What are some examples of principle of moments
Seesaw a and balance scales
What does the force exerted by a hydraulic pressure system depend on
The force exerted on the system
The area of the cylinder on which this force acts
The area of the cylinder that exerts the force
Why can hydraulic systems be used as a force multiplier
The use of different cross sectional areas on the effort and load sides of the system mean it can be used as a force multiplier
When an object moves in a circle it is constantly moving in a different direction…….
So it is continuously changing velocity
What is centripetal acceleration
The acceleration of an object moving in a circle acting on a object moving in a circular path which always acts towards the centre of the circle
If the centripetal force stops acting …….
The object will continue to move in a straight line at a tangent to the circle
the centripetal force needed to make an object perform circular motion increases as …..
The mass of the object increases
The speed of the object increases
The radius of the circle decreases
What is oscillating motion
Moving to and fro along the same line
What does a simple pendulum consist of
A mass, called a bob suspended on the end of a string
What happens when the Bob is displaced to one side and let go
The pendulum oscillates back and forth through the equilibrium position
What is The amplitude of the oscillation
The distance from the equilibrium position to the highest position on either side
What is the time period of the oscillation
The time taken for one complete cycle which is
The time taken from the highest position on one side to the highest position on the other side and back to the start position
The time taken between successive passes in the same direction through the equilibrium position.
How do you calculate the time period
To measure the time period of a pendulum we can measure the average time for 20 oscillations and divide the timing by 20
What does the time period depend on
The length of the pendulum and increase as its length increases
What is the frequency of the oscillations
The number of complete cycles of oscillation per second
Why will a swing come to rest if not pushed
Energy is transferred due to friction at the top of the swing and due to air resistance
