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Forces in Balance-Revision- - Coggle Diagram
Forces in Balance-Revision-
vectors and scalars
Scalars have size (magnitude) without direction.
Examples: Distance, speed, mass, energy, density, power and temperature
Vectors have both size (magnitude) and direction. :
Examples: Displacement, velocity, weight, acceleration, force, pressure, momentum , gravity and drag
levers and gears
A lever consists of : a pivot , an effort and a load
A simple lever could be a solid beam laid across a pivot. As effort is applied to rotate one end about the pivot. The opposite end is also rotated about the pivot in the same direction. This has the effect of rotating or lifting the load.
Levers, such as this one, make use of moments to act as a force multiplier. They allow a larger force to act upon the load than is supplied by the effort, so it is easier to move large or heavy objects.
Force multipliers: lever are easier use with long spanner or a gear is good to x2 the force multiplier
The longer the lever, and the further the effort acts from the pivot, the greater the force on the load will be. It is easier to use a longer spanner when trying to turn a nut, and easiest to push furthest from the hinge when opening a door.
Moments and Equilibrium
All the forces acting on an object that don't pass through a fixed point can turn an object about that point
The direction of the force and the position of the fixed point determines whether the moment acts clockwise or anticlockwise
If an object at rest doesn't turn the sum of the anticlockwise moments about any point = the sum of the clockwise moments at that point
Formulas:
:explode:
speed= distance/time
acceleration= change in velocity/time
v^2 - u^2 =2as (final velocity^2-initial velocity^2= 2 x speed x acceleration)
Resultant Force = mass x acceleration
Force = spring constant x extension
Work done = force x distance
pressure= force on surface/area of surface
moment = perpendicular force x distance
Free body diagrams
:pencil2:
Free force body are designed to tell us what forces are involved.
Drag
Gravity
Thrust
lift
Forces between objects
Force is measured in newtons(N).
When two objects interact, they always exert equal and opposite forces on each other
When two objects attract that means that they have the opposite forces.
Resultant forces
The resultant force of an object is a single force that has the same effect as all the forces acting on the object
Greater than zero, the speed or direction of the object will change
Their sum will equal, if the forces act in the same direction
Resultant force: Zero, the object stays at rest or at the same speed and direction
Their difference, if the forces act in opposite direction
Centre of mass
The centre of mass of an object is the point through which all the masses appears to be connected.
For a symmetrical object the centre of mass would be when along the axis of symmetry .
if an object is suspended and then released,it will come to rest with its centre of mass directly below the point of suspension.
The parallelogram of forces
We can use a parallelogram to calculate the resultant force.
We can do this by using a compass and measuring a scale.
Resolution of forces
How to resolve forces:;
Resolving horizontally and vertically.
A vertical force has no horizontal component and a horisontal force has no vertical component.
we normally choose upwards and then to the right as our positive directions.
To do this we will need to use trigonometry
Experiment :
Plan an experiment to investigate the effects of different lubricants on friction:
Equipment: string, weight, different lubrication, block
risk assessment: mass and glider falling. The consequence is that objects can fall on your feet and cause a bruise or fracture. To control this you should use relatively small masses and step back after releasing the glider.
Variables:
Dependent: the weights
Independant: the type of lubricant and the weights
controlled: same amount of lubrication and the same length of string
Method:
On a box apply one type of lubricant on one side.
Place the applied side face flat on the wooden surface
Then with the string, tie it to the box
Tie the weight on the other end.
One by one add the weights until the box moves.
Errors:
could be the wrong amount of lubricant
not putting the box at the same place
