3- Making Things Work Flashcards
What can be done to increase the moment of the force?
Force must increase
The distance to the pivot must increase
What is an everyday example of moments?
It is easier to undo a wheel-nut by pushing on the end of a long spanner than a short one because the distance from the pivot is greater
What is a moment?
The turning effect of a force
What is the 1) load 2) effort?
1) the force we are trying to move
2) the force applied
Because of the lever, the effort can be much less than the load
What is the centre of mass?
Where particles mass are concentrated at a point on an object
What is object equilibrium?
An object freely suspended (balanced) - it’s centre of mass is directly below the point of suspension
The clockwise and anticlockwise moments are equal
How do you find the centre of mass of a thin irregular sheet of material (randomly cut sheet of paper)?
Suspend the sheet from a pin held in a clamp stand (make sure it’s static)
Hang a plumbline from the same pin and mark it’s position on the sheet
Hang the sheet from another point and repeat - the centre of mass is where the plumblines cross
Where is the centre of mass for a symmetrical object?
Along the axis of symmetry or where the axis of symmetry meet
What are examples of the principle of moments?
Seesaw, balance scale
Where does the line of action of the weight act?
Through it’s centre of mass
If it acts outside the base, the object will topple ((resultant moment)
What makes an object more stable?
A wider base
Lower centre of mass
(It has to tilt further before the line of action is outside the base)
About liquids in terms of pressure?
Virtually incompressible
Pressure transmitted equally in all directions
Force exerted at one point will be transmitted to other points
Makes use of hydraulic pressure systems
What is the force exerted by hydraulic pressure systems dependent on?
The force exerted on the system
The area of the cylinder at which the force acts on
The area of the cylinder that exerts the force
How can a hydraulic system be used as a force multiplier?
The use of different cross sectional areas on the effort and load sides of the hydraulic system
What is centripetal acceleration?
When an object moves in a circle (continuously changing direction/velocity) - meaning it is accelerating
What is the centripetal force?
The resultant force that always acts towards the centre of the circle when an object is moving in a circle
What happens in the centripetal force stops acting?
The object will continue to move in a straight line - a tangent to the circle it was making
How can the centripetal force increase?
The mass of the object increases
The speed of the object increases
The radius of the circle decreases
What forces can provide centripetal force?
Gravitational force
Electric force
Tension
What is an example of oscillating motion?
A pendulum moving to and fro along the same line
What is the equilibrium position on a pendulum?
The position of the pendulum when it stops moving completely
Describe the functions of a simple pendulum?
A mass (called a bob) on the end of a string. When the bob is displaced to one side and let go, the pendulum oscillates back and forth, through the equilibrium
WhT is the amplitude in terms of a pendulum?
The distance from the equilibrium to the highest position on either side
What are the two ways time period of a pendulum can be measured?
Time taken from one highest point to the other and back to the equilibrium
Time taken between successive passes in the same direction through the equilibrium
(Measure either action 20times and then divide by 20 for the average)
What is the only way to increase the time period on pendulum?
Increase the length of the string of the pendulum
What is the frequency of a pendulum?
The number of complete cycles of oscillation per second
An example of a pendulum?
A playground swing
