Forces Flashcards
What can force be describes as?
A push or a pull
What happens when a force acts on an object?
It will try to move the object or change its direction or speed.
Forced can also change the shape of an object.
What is the size of a force measured in?
Newton’s
What is a force?
A vector
What are the 4 forces that act on a plane?
Lift ⬆️
Weight/gravity⬇️
Thrust➡️
Drag/air resistance⬅️
What does Hooke’s law state?
This is only true if…
Up to the limit of a proportion the extension of a helical spring is directly proportional to the load applied.
Only true if the spring is not stretched beyond a point called the limit of proportionality.
A spring stretched beyond its elastic limit will not return to its original length as it has been permanently stretched.
What is the equation for hook’s law?
F = K x E (F = force) (K = spring constant/stiffness) (E = extension)
How can you write hooks law as a ratio?
F1 e1
— = —
F2 e2
Four examples of compression type springs?
Bed mattress
Pens
Car suspension
Trampoline
What is the turning effect of a force called?
What is the point where the object is fixed called?
A moment
The pivot
What does the size of the turning effect or moment produced by a force depend on?
The size of the force and the distance between the force and the pivot.
How can we work out the size of the moment?
Moment = force x distance from pivot (perpendicular)
M=FxD
What are the units for a moment?
Nm or Ncm
What is the principle of moments?
When a system is in equilibrium the sum of the moments in the clockwise direction are equal to the sum of moments in the anti-clockwise direction about a fixed point.
The principle of moments tells us what happens when a lever with several forces acting on it is balanced or in equilibrium.
What is the clockwise moment equal to?
The anti-clockwise moment
Wha happens when a load is closer or further away from the pivot?
The closer the load is to the pivot the smaller it’s turning effect/moment will be.
A smaller moment will not require as large a force.
What is an objects centre of gravity?
The point where the total weight of the body appears to act.
If the object is a regular shape then the centre of gravity will be at the centre of the object.
What is the centre of mass?
This is the point where it’s total mass appears to act.
Unless an object is very large the centre of mass and centre of gravity will be at the same point.
How can the stability of an object be increased?
Lower the centre of gravity
Widen the base of the object
What happens when a force acts on an object?
It exerts pressure on the object
What does the amount of pressure depend on?
The size of the force and the area over which the force acts.
The smaller the are , the greater the pressure.
The greater the are, the smaller the pressure.
Define pressure
Force applied per unit surface area
Eg. Newton’s per metre squared (N/m(2))
Equation for pressure?
Pressure = force/area
F
P x A
What is another word for N/m(2)
Pascals
Are liquids compressible or incompressible?
Incompressible
Because of this they are used to transfer pressure
