C4 (Forces in Action) Flashcards
What does the mass of an object depend on
Amount of matter it cotains
A net force acting on the object will make the object will make it…
Accelerate if the direction of the net force
Equation for resultant force
F=ma
Equation for weight
W=mg
Where would the resultant force on the object (it’s total weight) will act through a point often called…
The objects centre of gravity
Why do we use the centre of mass
Much easier to analyse and solve physics problems
How do you find the centre of gravity
Using a plumb line
Weight
The gravitational force acting on an object through its centre of mass
Friction
The force that arises when two surfaces rub against each other
Drag
The resistive force on an object travelling through a liquid, the same as friction
Tension
The force within a stretched cable or rope
Normal contact force
A force arising when one object rests against another object
Normal means at a right angle too
Assuming there’s no friction what’s the only force acting on an object
It’s weight
Which can be resolved into two components, parallel and perpendicular to the slope.
An object moving through an object experiences what
Drag
Drags magnitude depends on several factors…
Speed of object
Shape of object
Roughness and texture
Density of the fluid through which it travels
Most important factors are it’s speed and cross sectional area
What is drag directly proportional to?
Speed^2
What does having a vehicle that’s more smooth and streamline permit
Increase top speed and reduces the amount of fuel used on a journey
Terminal velocity
When the drag force on the object is equal and opposite to it’s weight . At terminal velocity the object has zero acceleration and it’s speed is constant.
Moment of a force
The turing effect of a force about some axis or point
Moment equation
Moment= force x perpendicular distance of the line of action form the axis/point of rotation
The principal of moments
When body is in equilibrium the net force and it’s net moment is 0.
For a body in rotational equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of the clockwise moments about the same point.
Torque of a couple
One of the forces x perpendicular separation between the forces
=Fd
Torque
A moment of a couple
Couple
Two forces that must be parallel and along different lines.
How can forces in equilibrium be drawn
Triangle of forces ( an enclosed triangle as the forces are in equilibrium)
Density
Mass per unit of volume
Density=m/v
Pressure equation
Pressure = Force/ Area
What are fluids
Substances that can flow
How to calculate pressure exerted by a vertical column of any liquid
p= height x density x gravitational potential
The pressure in a fluid at any particular depth has an unusual feature are
It is the same in all directions
Upthrust is based on what
Pressure difference
Archimedes principle
The upthrust exerted on a body immersed in a fluid, wether fully or partially submerged, is equal to the weight of the fluid that the body displaces
When will an object sink
If the upthrust is less than the weight of the object
Density
Is the mass per unit volume
Pressure
Is the force per unit area
2 equations for pressure
P=F/A
P=hpg
Upthrust
An upward force that fluids excerpt on objects that are partially or fully submerged in the fluid. Occurs because of the pressure difference between the top and bottom of the object.
Upthrust is equal to…
The weight of the fluid displaced
Archimedes’s principle
Says that when a body is completely or partially immersed it experiences an upthrust equal to the weight of the fluid it has displaced
Power equation
Power= Force x Velocity
Most car safety features are designed to slow you down gradually
Give some examples
Seat belts
Air bags
Crumple zones
