Topic 9 - Forces And Effect Flashcards
What is a force?
A push or pull acting on an object due to an interaction with another object.
What are two categories that all forces can be split into?
Contact forces (objects touching) Non-contact (objects seperated)
Three examples of contact forces
Friction
Air resistance
Tension
Three examples of non-contact forces
Gravitational forces
Electrostatic forces
Magnetic forces
Is force a vector or a scalar quantity? Why?
Vector
It has both magnitude and direction
What is a scalar quantity?
A quantity that only has magnitude no direction
What is a vector quantity?
A quantity that has both magnitude and direction.
Three examples of vector quantities
Velocity
Displacement
Force
Three examples of scalar
Temperature Time Mass Speed Distance Energy
What magnitude would the resultant force have and in what direction would it be pointing?
What is the name for the turning effect of a force?
A moment
State the equation used to calculate the moment of a force
Moment of force = force x perpendicular distance of force from the pivot
Momemt (Nm/newton meters)
Force (N)
Distance (m)
What distance do we use when calculating a moment?
The perpendicular distance from the pivot to the line of action of the force (line drawn of the force).
An object is in equilibriumm, what does this say about the moments acting on the objects?
The clockwise moments are equal to the anti-clockwise moments.
How do levers make use of moments?
They increase perpendicular distance of the force from the pivot, so decrease the force needed to produce the same moment.
Will this object rotate? If yes, what direction?
No. The clockwise and anti-clockwise moments are equal, therefore the object remains in equilibrium.
How are levers used to decrease the force required to lift something?
Levers use a pivot point and the concepts of moments to reduce the force. The further you are away from the pivot point, the less force you need to lift the object up.
How does lubricating levers/gears improve efficiency?
There is less resistance; less energy is wasted/dissipated (as heat) overcoming frictional forces.
When does rotation occur?
If an object is attached to a pivot point - a point it can rotate about, but cannot move away
And a force is applied perpendicular to the object - it will move about the pivot in this direction
If its not applied perpendicular to the object, find the perpendicular distance from the pivot to see which way it will turn
If the force is applied not towards the point, the object will not rotate.
